UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUERPURSUANT TO RULE 13a-16 OR 15d-16
UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of November 2025

Commission File Number: 001-41858

Okeanis Eco Tankers Corp.

(Translation of registrant’sname into English)

c/oOET Chartering Inc., Ethnarchou Makariou Ave., & 2 D. Falireos St., 185 47 N. Faliro, Greece

(Address of principal executiveoffice)

Indicate by check mark whether the registrant filesor will file annual reports under cover of Form 20-F or Form 40-F:

Form20-F x Form 40-F ¨

INFORMATION CONTAINED IN THISFORM 6-K REPORT

Attachedto this report on Form 6-K as Exhibit 99.1 is a copy of the press release publishedby Okeanis Eco Tankers Corp. on November 19, 2025, titled “OkeanisEco Tankers Corp. – Reminder of trading suspension on Euronext Oslo Børs.”

Attachedto this report on Form 6-K as Exhibit99.2 is a copy of the press release published by Okeanis Eco Tankers Corp. on November 19, 2025, titled “Okeanis EcoTankers Corp. – Completion and pricing of USD 115 million offering of new commonshares.”

Thisreport on Form 6-K shall not constitute an offer to sell or the solicitationof an offer to buy the securities discussed herein, nor shall there be any offer, solicitation, or sale of the securities in any statein which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any suchstate.

Thisreport on Form 6-K and the exhibits hereto are hereby incorporated by reference into the registrant’s registrationstatements: (A) on Form F-3 (File No. 333-287032), filed with the Securities andExchange Commission on May 7, 2025 and declared effective on May 21, 2025 and (B) on Form F-3 (File No. 333-287036), filed with the Securities and Exchange Commission on May 7, 2025 and declared effective on May 21,2025.

SIGNATURES

Pursuant to the requirements ofthe Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereuntoduly authorized.

Date:November 19, 2025

Exhibit 99.1

Okeanis Eco Tankers Corp. – Reminderof trading suspension on Euronext Oslo Børs

ATHENS, GREECE, 19 November 2025 –Okeanis Eco Tankers Corp. ( “OET” or the “Company”) (NYSE: ECO, OSE: OET) has announced a contemplatedoffering of new common shares (the “Offering”).

This is a reminder that a trading halt will beimposed on the Company’s common shares that are trading on Euronext Oslo Børs today, 19 November 2025, from openingof trade until 13:00 CET, to facilitate an efficient bookbuilding process for the Offering.

A separate announcement regarding the bookbuildingprocess for the Offering is expected to be made later today, prior to commencement of trading of the Company’s shares on EuronextOslo Børs.

Contacts

Company:

Iraklis Sbarounis, CFO 

Tel: +30 210 480 4200 

ir@okeanisecotankers.com

Investor Relations / Media Contact:

Nicolas Bornozis, President 

Capital Link, Inc. 

230 Park Avenue, Suite 1540, New York, N.Y.10169 

Tel: +1 (212) 661-7566 

okeanisecotankers@capitallink.com

About OET

OET is a leading international tanker companyproviding seaborne transportation of crude oil and refined products. The Company was incorporated on 30 April 2018 under the lawsof the Republic of the Marshall Islands and is listed on Oslo Stock Exchange under the symbol OET and the New York Stock Exchange underthe symbol ECO. The sailing fleet consists of six modern scrubber-fitted Suezmax tankers and eight modern scrubber-fitted VLCC tankers.

Important Note

The information contained in this announcementis for background purposes only and does not purport to be full or complete. No reliance may be placed for any purpose on the informationcontained in this announcement or its accuracy, fairness or completeness.

Neither this announcement nor the informationcontained herein is for publication, distribution or release, in whole or in part, directly or indirectly, in or into or from Australia,Canada, Japan, Hong Kong, South Africa or any other jurisdiction where to do so would constitute a violation of the relevant laws of suchjurisdiction. The publication, distribution or release of this announcement may be restricted by law in certain jurisdictions and personsinto whose possession any document or other information referred to herein should inform themselves about and observe any such restriction.Any failure to comply with these restrictions may constitute a violation of the securities laws of any such jurisdiction.

This announcementdoes not constitute an offer of securities for sale in the United States. Securities may not be offered or sold in the UnitedStates absent registration under the Securities Act of 1933, as amended, or an exemption from registration. Any public offering ofsecurities to be made in the United States will be made by means of a prospectus that may be obtained from the Companyand that will contain detailed information about the Company and management, as well as financial statements. In any EEA Member State,this communication is only addressed to and is only directed at qualified investors in that Member State within the meaning of the EUProspectus Regulation, i.e. only to investors who can receive the offer without an approved prospectus in such EEA Member State. The expression"EU Prospectus Regulation" means Regulation (EU) 2017/1129 of the European Parliament and of the Council of 14 June 2017(together with any applicable implementing measures in any Member State).

This communication is only being distributed toand is only directed at persons in the United Kingdom that are "qualified investors" within the meaning of the EU ProspectusRegulation as it forms part of English law by virtue of the European Union (Withdrawal) Act 2018 and that are (i) investment professionalsfalling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the"Order") or (ii) high net worth entities, and other persons to whom this announcement may lawfully be communicated, fallingwithin Article 49(2)(a) to (d) of the Order (all such persons together being referred to as "relevant persons").This communication must not be acted on or relied on by persons who are not relevant persons. Any investment or investment activity towhich this communication relates is available only to relevant persons and will be engaged in only with relevant persons. Persons distributingthis communication must satisfy themselves that it is lawful to do so.

Forward-Looking Statements

This communication contains “forward-lookingstatements”, including as defined under applicable laws, such as the US Private Securities Litigation Reform Act of 1995. Forward-lookingstatements provide the Company’s current expectations or forecasts of future events. Forward-looking statements include statementsabout the Company’s expectations, beliefs, plans, objectives, intentions, assumptions and other statements that are not historicalfacts or that are not present facts or conditions. Words or phrases such as “anticipate,” “believe,” “continue,”“estimate,” “expect,” “hope,” “intend,” “may,” “ongoing,” “plan,”“potential,” “predict,” “project,” “should,” “will” or similar words or phrases,or the negatives of those words or phrases, may identify forward-looking statements, but the absence of these words does not necessarilymean that a statement is not forward-looking. Forward-looking statements are subject to known and unknown risks and uncertainties andare based on potentially inaccurate assumptions that could cause actual results to differ materially from those expected or implied bythe forward-looking statements. The Company’s actual results could differ materially from those anticipated in forward-looking statementsfor many reasons, including as described in the Company’s filings with the SEC. Accordingly, you should not unduly rely on theseforward-looking statements, which speak only as of the date of this communication. Factors that could cause actual results to differ materiallyinclude, but are not limited to, the Company’s operating or financial results; the Company’s liquidity, including its abilityto service its indebtedness; competitive factors in the market in which the Company operates; shipping industry trends, including charterrates, vessel values and factors affecting vessel supply and demand; future, pending or recent acquisitions and dispositions, businessstrategy, areas of possible expansion or contraction, and expected capital spending or operating expenses; risks associated with operations;broader market impacts arising from war (or threatened war) or international hostilities; risks associated with pandemics, including effectson demand for oil and other products transported by tankers and the transportation thereof; and other factors listed from time to timein the Company’s filings with the SEC. Except to the extent required by law, the Company expressly disclaims any obligations orundertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in theCompany’s expectations with respect thereto or any change in events, conditions, or circumstances on which any statement is based.You should, however, review the factors and risks the Company describes in the reports it files and furnishes from time to time with theSEC, which can be obtained free of charge on the SEC’s website at www.sec.gov.

Exhibit 99.2

Okeanis Eco Tankers Corp. – Completionand pricing of USD 115 million offering of new common shares

ATHENS, GREECE, 19 November 2025 –Okeanis Eco Tankers Corp. (the “Company” or “OET”) (NYSE: ECO, OSE: OET) is pleased to announce thatfollowing strong demand it has successfully priced an offering of 3,239,436 new shares of the Company’s common stock, parvalue USD 0.001 per share (the “Offer Shares”), at a price of USD 35.50 per Offer Share, raising gross proceeds of USD114,999,978 (the “Offering”).

The net proceeds from the Offering are expectedto be used as partial consideration for the acquisition of two newbuilding Suezmax vessels (the “Vessel Acquisitions”),each currently under construction at Daehan Shipbuilding Co., Ltd., a South Korean shipyard, each from an unrelated third-party seller,for an acquisition price of USD 97 million per vessel. Each vessel is expected to be delivered from the shipyard in January 2026,subject to satisfaction of closing conditions for such delivery. If one or both of the Vessel Acquisitions do not consummate, the netproceeds from the Offering may be used for general corporate purposes.

The Offering is expected to be completed by deliveryof the allocated Offer Shares to investors through the Depository Trust Company (DTC) on a delivery vs payment basis on or about 21 November 2025,subject to the satisfaction of customary closing conditions, including that the agreements for the Vessel Acquisitions remaining in fullforce and effect at the time of closing. The Offer Shares will be available for trading on New York Stock Exchange once the Offer Shareshave been issued and settlement has taken place, expected on or about 21 November 2025.

The Company has considered the Offering in lightof the equal treatment obligations under the Norwegian Securities Trading Act section 5-14, and the Board is of the opinion that the Offeringis in compliance with these requirements.

The Offering is being made pursuant to the Company’sshelf registration statement on Form F-3 (File No. 333-287032), which was declared effective by the U.S. Securities and ExchangeCommission (the “SEC”) on 21 May 2025. The Offering is being made only by means of a prospectus supplement preparedspecifically in relation to the Offering, which was filed with the SEC under Rule 424(b) under the U.S Securities Act of 1933and can be obtained at www.sec.gov. Electronic copies of the prospectus supplement and related prospectus may also be obtained by contactingFearnley Securities AS at prospectus@fearnleys.com or Clarksons Securities AS at compliance.oslo@clarksons.com. A final prospectussupplement is expected to filed with the SEC and made available at www.sec.gov.

This announcement is for information purposesonly and does not constitute or form part of an offer to sell or the solicitation of an offer to purchase or subscribe for securities,nor will there be any sale of the securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior tothe registration or qualification under the securities laws of any such jurisdiction. Any offers, solicitations or offers to buy, or anysales of securities will be made in accordance with the registration requirements of the Securities Act of 1933, as amended.

Advisors

Fearnley Securities AS is acting as global coordinatorand joint bookrunner, and Clarksons Securities AS is acting as joint bookrunner, for the Offering (collectively referred to as the “Managers”).Fearnley Securities AS is not a U.S. registered broker-dealer, and to the extent that this offering is made within the United States,its activities will be effected only to the extent permitted by Rule 15a-6 of the Securities Exchange Act of 1934, as amended orthrough its affiliate Fearnley Securities Inc. Clarksons Securities AS is not a U.S. registered broker-dealer and to the extent that thisoffering is made within the United States, its activities will be effected only to the extent permitted by Rule 15a-6 of the SecuritiesExchange Act of 1934, as amended or through its affiliate Clarksons Securities, Inc.

Contacts

Company:

Iraklis Sbarounis, CFO

Tel: +30 210 480 4200

ir@okeanisecotankers.com

Investor Relations / Media Contact:

Nicolas Bornozis, President

Capital Link, Inc.

230 Park Avenue, Suite 1540, New York, N.Y. 10169

Tel: +1 (212) 661-7566

okeanisecotankers@capitallink.com

This information is considered to be inside informationpursuant to article 7 of the EU Market Abuse Regulation and is subject to the disclosure requirements pursuant to article 17 of the EUMarket Abuse Regulation and section 5-12 the Norwegian Securities Trading Act.

This stock exchange release was published on theOslo Stock Exchange by Irene Chaidemenou, Legal Counsel, Okeanis Eco Tankers Corp., on the date and time provided.

About OET

OET is a leading international tanker companyproviding seaborne transportation of crude oil and refined products. The Company was incorporated on April 30, 2018 under the lawsof the Republic of the Marshall Islands and is listed on Oslo Stock Exchange under the symbol OET and the New York Stock Exchange underthe symbol ECO. The sailing fleet consists of six modern scrubber-fitted Suezmax tankers and eight modern scrubber-fitted VLCC tankers.

Important information

The information contained in this announcementis for background purposes only and does not purport to be full or complete. No reliance may be placed for any purpose on the informationcontained in this announcement or its accuracy, fairness or completeness.

Neither this announcement nor the informationcontained herein is for publication, distribution or release, in whole or in part, directly or indirectly, in or into or from the Australia,Canada, Japan, Hong Kong, South Africa or any other jurisdiction where to do so would constitute a violation of the relevant laws of suchjurisdiction. The publication, distribution or release of this announcement may be restricted by law in certain jurisdictions and personsinto whose possession any document or other information referred to herein should inform themselves about and observe any such restriction.Any failure to comply with these restrictions may constitute a violation of the securities laws of any such jurisdiction.

This announcement does not constitute an offerof securities for sale in the United States. Securities may not be offered or sold in the United States absent registration under theSecurities Act of 1933, as amended, or an exemption from registration. Any public offering of securities to be made in the United Stateswill be made by means of a prospectus that may be obtained from the Company and that will contain detailed information about the Companyand management, as well as financial statements.

In any EEA Member State, this communication isonly addressed to and is only directed at qualified investors in that Member State within the meaning of the EU Prospectus Regulation,i.e. only to investors who can receive the offer without an approved prospectus in such EEA Member State. The expression "EU ProspectusRegulation" means Regulation (EU) 2017/1129 of the European Parliament and of the Council of 14 June 2017 (together with anyapplicable implementing measures in any Member State).

This communication is only being distributed toand is only directed at persons in the United Kingdom that are "qualified investors" within the meaning of the EU ProspectusRegulation as it forms part of English law by virtue of the European Union (Withdrawal) Act 2018 and that are (i) investment professionalsfalling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the"Order") or (ii) high net worth entities, and other persons to whom this announcement may lawfully be communicated, fallingwithin Article 49(2)(a) to (d) of the Order (all such persons together being referred to as "relevant persons").This communication must not be acted on or relied on by persons who are not relevant persons. Any investment or investment activity towhich this communication relates is available only to relevant persons and will be engaged in only with relevant persons. Persons distributingthis communication must satisfy themselves that it is lawful to do so.

Forward-Looking Statements

This communication contains “forward-lookingstatements”, including as defined under applicable laws, such as the US Private Securities Litigation Reform Act of 1995. Forward-lookingstatements provide the Company’s current expectations or forecasts of future events. Forward-looking statements include statementsabout the Company’s expectations, beliefs, plans, objectives, intentions, assumptions and other statements that are not historicalfacts or that are not present facts or conditions. Words or phrases such as “anticipate,” “believe,” “continue,”“estimate,” “expect,” “hope,” “intend,” “may,” “ongoing,” “plan,”“potential,” “predict,” “project,” “should,” “will” or similar words or phrases,or the negatives of those words or phrases, may identify forward-looking statements, but the absence of these words does not necessarilymean that a statement is not forward-looking. Forward-looking statements are subject to known and unknown risks and uncertainties andare based on potentially inaccurate assumptions that could cause actual results to differ materially from those expected or implied bythe forward-looking statements. The Company’s actual results could differ materially from those anticipated in forward-looking statementsfor many reasons, including as described in the Company’s filings with the SEC. Accordingly, you should not unduly rely on theseforward-looking statements, which speak only as of the date of this communication. Factors that could cause actual results to differ materiallyinclude, but are not limited to, the Company’s operating or financial results; the Company’s liquidity, including its abilityto service its indebtedness; competitive factors in the market in which the Company operates; shipping industry trends, including charterrates, vessel values and factors affecting vessel supply and demand; future, pending or recent acquisitions and dispositions, businessstrategy, areas of possible expansion or contraction, and expected capital spending or operating expenses; risks associated with operations;broader market impacts arising from war (or threatened war) or international hostilities; risks associated with pandemics, including effectson demand for oil and other products transported by tankers and the transportation thereof; and other factors listed from time to timein the Company’s filings with the SEC. Except to the extent required by law, the Company expressly disclaims any obligations orundertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in theCompany’s expectations with respect thereto or any change in events, conditions, or circumstances on which any statement is based.You should, however, review the factors and risks the Company describes in the reports it files and furnishes from time to time with theSEC, which can be obtained free of charge on the SEC’s website at www.sec.gov.