UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TORULE 13a-16 OR 15d-16
UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of December, 2025.

Commission File Number: 001-41566

DEFSECTechnologies Inc.

(Exact Name of Registrant as Specified in Charter)

80 Hines Rd, Suite 300, Ottawa, Ontario,K2K 2T8

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annualreports under cover Form 20-F or Form 40-F.

Form 20-F x  Form 40-F ¨

SIGNATURE

Pursuant to the requirements of the SecuritiesExchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

EXHIBIT INDEX

Exhibit 99.1

DEFSEC TechnologiesAnnounces Significant Momentum in Revenue Growth due to Increased Annualized Billings for Government Services on a Go-Forward Basis toApproximately CAD$8.3M Commencing February 2026

Ottawa,Ontario, December 5, 2025 - DEFSEC Technologies Inc. (TSXV: DFSC) (TSXV: DFSC.WT.U) (NASDAQ:DFSC) (NASDAQ: DFSCW) ("DEFSEC" or the "Company") is pleased to announce significant momentum in itsgovernment services business as it expects to add an additional 15 roles to the 24 roles previously disclosed in the Company's news releasedated October 29, 2025, for a total of 39 roles staffed commencing in February, 2026. All dollar amounts in this news release arein Canadian Dollars unless otherwise noted.

All roles havebeen staffed with a large part of the increase due to an expansion of work scope with the Directorate Land Command Systems Program ManagementSoftware Engineering Facility (“DSEF”) contract for digital modernization of the Canadian Armed Forces.

DEFSEC has arrangedto fast track the fulfillment of this new work scope requirement by subcontracting 13 of the additional 15 roles from ADGA Group ConsultantsInc. (“ADGA”). Commencement of work in February 2026 is subject to customary administrative onboarding procedures.The Company has already received DSEF’s statement of work and expects to complete onboarding procedures over the next several weeksin time for the February start.

¹ See Consolidated Financial Statements of DEFSEC TechnologiesInc. (Formerly KWESST Micro Systems Inc.) for the years ended September 30, 2024, 2023 and 2022 filed on the Company’s SEDAR+ profileat https://sedarplus.ca/.

² Unaudited, non-IFRS measure. See"Non-IFRS Measures" below.

³ Unaudited, as published financial statements do not disclosegross margin by product line.

Thecumulative impact of the additional resources means that, effective February 2026, when work commences, the Company’s go-forwardannualized program billings are expected to increase to approximately $8.3M⁴, comparedto the $5.1M⁵ as reported in Company's news release datedOctober 29, 2025. Additionally, annualized gross margins on a go-forward basis on programmatic work are expected to increase commensuratelyto approximately $2.3M (with approximately $0.5M of the increase in gross margin associated with the roles added since October 29,2025). This moves the Company significantly further towards its goal of achieving a cash flow positive operation on the commercializationof its technology and resources.

“It’s very gratifying to see the continuedmomentum in our programmatic work on digital modernization of the Canadian Armed Forces with our industry partners,” said Sean Homuth,DEFSEC President and CEO. LGen Jean-Marc Lanthier (Ret’d), President and CEO of ADGA, commented that “ADGA brings experiencedsoftware development experts who have supported DND for many years. We look forward to continuing to deploy this operationally criticaltalent in collaboration with DEFSEC so the customer benefits from teams ready to deliver without delay.”

“Theannouncement today means that DEFSEC’s annualized go-forward revenue run rate of approximately $8.3M at the beginning in February 2026are expected to be approximately 704% higher than our actual Fiscal 2024 programmatic revenue of $1.0M,” added Mr. Homuth. “Additionally, partnering with ADGA will have the effect of an immediate impact on revenue and margin when this additional, ongoingwork commences in February 2026.”

Mr. Homuthconcluded by noting that “This collaboration with ADGA is a great example of two Canadian defence companies working togetherto quickly deliver upgraded capability to our Canadian Armed Forces. We continue to be well positioned for further momentum and growthas the Canadian government works to increase defence spending on critical capabilities within our sphere of expertise”.

The Company noted that these updated go-forwardrevenue run rate and margin contribution numbers announced today exclude its product business, principally ARWEN sales, which are projectedto increase significantly in Fiscal 2025 over Fiscal 2024. The Company expects further revenue growth as the Canadian government continuesto put action to their planned defense spending and increased margins as the Company continues to scale its programmatic services.

While the Company expects to file its year-endfilings shortly, they will largely be in line with the Q3 growth trajectory and will present a strong financial position owing to thefinancing completed in Q4.

⁴ Unaudited, non-IFRS measure. See "Non-IFRS Measures"below. Also includes impact of annual escalation of rates billed.

⁵ Unaudited, non-IFRS measure. See "Non-IFRS Measures"below.

David Luxton, Chairman

luxton@defsectec.com

Sean Homuth, President and ChiefExecutive Officer

homuth@defsectec.com

Jennifer Welsh, Chief FinancialOfficer and Chief Compliance Officer

welsh@defsectec.com

Jason Frame, Investor Relations

+1 (587) 225-2599

frame@defsectec.com

About DEFSEC

DEFSEC (TSXV: DFSC and DFSC.WT.U;NASDAQ: DFSC and DFSCSW; FSE: 62UA) develops and commercializes breakthrough next-generation tactical systems for military and securityforces.   The company’s current portfolio of offerings includes digitization of tactical forces for real-time sharedsituational awareness and targeting information from any source (including drones) streamed directly to users’ smart devices andweapons. Other DEFSEC products include countermeasures against threats such as electronic detection, lasers and drones. These systemscan operate stand-alone or integrate seamlessly with OEM products and battlefield management systems, and all come integrated with TAK.The company also has a new proprietary non-lethal product line branded PARA SHOT^TM with applications across all segmentsof the non-lethal market, including law enforcement.  The Company is headquartered in Ottawa, Canada, with a representative officein London, UK.

Formore information, please visit https://www.defsectec.com 

Forward-Looking Statements

This press release contains “forward-looking statements” and “forward-looking information” within the meaning of Canadian and United Statessecurities laws (collectively, “forward-looking statements”), which may be identified by the use of terms and phrasessuch as “may”, “would”, “should”, “could”, “expect”, “intend”, “estimate”, “anticipate”, “plan”, “foresee”, “believe”, or “continue”,the negative of these terms and similar terminology, including references to assumptions, although not all forward-looking statementscontain these terms and phrases. Forward-looking statements made by DEFSEC in this press release include, but are not limited to, thetiming and impact on DEFSEC's revenue and gross margins resulting from its agreements with ADGA, projected increases of ARWEN sales, growthof DEFSEC's revenue and gross margins resulting from the Canadian government's planned defense spending and DEFSEC's programmatic servicesscaling, the timeline for DEFSEC’s programmatic services scaling, and the timing and contents of DEFSEC's year-end financial statements.Forward-looking statements are provided for the purpose of assisting the reader in understanding us, our business, operations, prospectsand risks at a point in time in the context of historical and possible future developments and therefore the reader is cautioned thatsuch information may not be appropriate for other purposes. Such forward-looking statements are based on the current expectations of DEFSEC’smanagement and are based on assumptions and subject to risks and uncertainties.

Although DEFSEC’s managementbelieves that the assumptions underlying such forward-looking statements are reasonable, they may prove to be incorrect. The forward-lookingstatements discussed in this press release may not occur by certain specified dates or at all and could differ materially as a resultof known and unknown risk factors and uncertainties affecting DEFSEC, including, but not limited to,

DEFSEC's continued and successfulpartnership with ADGA through its agreements and its impacts on DEFSEC's revenue and gross margins, the timing and impact on DEFSEC'srevenue and gross margins resulting from its agreements with ADGA, the Canadian government's planned defense spending occurring as expectedor expressed, the ability of DEFSEC to scale its programmatic services scaling successfully, if at all, the ability of DEFSEC to fileits year-end financial statements on planned timelines, DEFSEC’s inability to secure contracts and subcontracts (on the timelines,size and scale expected or at all); amendments to statements of work and orders for its products in 2025 and onwards for reasons beyondits control; the renewal or extension of agreements beyond their original term; the granting of patents applied for by DEFSEC; inabilityto finance the scale up to full commercial production levels for its physical products; inability to secure key partnership agreementsto facilitate the outsourcing and logistics for its ARWEN and PARA SHOT products; inability to meet timeline to commercialization forSaaS product; overall interest in DEFSEC’s products being lower than anticipated, expected or expressed; general economic and stockmarket conditions; adverse industry events; future legislative and regulatory developments in Canada, the United States and elsewhere;the inability of DEFSEC to implement and execute its business strategies; risks and uncertainties detailed from time to time in DEFSEC’sfilings with the Canadian Security Administrators and the United States Securities and Exchange Commission; and other factors beyond thecontrol of DEFSEC.

Although DEFSEC has attemptedto identify important factors that could cause actual actions, events or results to differ materially from those described in forward-lookingstatements, there may be other factors that cause actions, events or results to differ from those anticipated, estimated or intended.Except as required by applicable securities laws, forward-looking statements speak only as of the date on which they are made and DEFSECundertakes no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future eventsor otherwise.

Neither the TSX Venture Exchangenor its respective Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibilityfor the adequacy or accuracy of this release.

Non-IFRS Measures

This news release makes referenceto certain non-IFRS measures. These measures are not recognized measures under the International Financial Reporting Standards (“IFRS”),do not have a standardized meaning prescribed by IFRS, and are therefore unlikely to be comparable to similar measures presented by othercompanies. Rather, these measures are provided as additional information to complement those IFRS measures by providing further understandingof our results of operations from management’s perspective. Accordingly, these measures should not be considered in isolation noras a substitute for analysis of our financial information reported under IFRS.

The non-IFRS measures usedin this news release. includes "annualized gross margin contribution" and "program billings on annualized go-forward basis",which are unaudited, non-IFRS measures.

"Annualized gross margincontribution", refers to gross margin dollars based on the staff and other related costs for the entire year at the program billingrate. Management believes annualized gross margin contribution is a useful measure because it aligns with annualized revenue and billings.The most directly comparable financial measure that is disclosed in the financial statements of the Company to which this non-IFRS measurerelates is gross margin.

"Program billings on annualizedgo-forward basis", refers to programmatic revenue based on the roles staffed for a full year at the program billing rate. Managementbelieves program billings on annualized go-forward basis is a useful measure because it reflects management’s estimate of annualizedrevenues based on current contractual taskings as of the date of this release. The most directly comparable financial measure that isdisclosed in the financial statements of the Company to which the non-IFRS measure relates is revenue.

These non-IFRS financial measuresreflect an additional way of viewing aspects of the Company’s operations that, when viewed with IFRS results and the reconciliationsto the corresponding IFRS financial measures, may provide a more complete understanding of factors and trends affecting the Company’sbusiness. Because non-IFRS financial measures exclude the effect of items that will increase or decrease the Company’s reportedresults of operations, management strongly encourages investors to review the Company’s consolidated financial statements and publiclyfiled reports in their entirety under the Company’s profile on EDGAR and SEDAR+.