The agreement is worth $531 million to Babcock Canada Inc., and could be extended past 2018 should the military decide to continue with the boats, which were purchased second-hand from the Royal Navy in the late 1990s.
The Conservatives initially awarded the controversial contract to the firm, the Canadian subsidiary of a British company, in 2008 after a legal fight with Irving Shipyards that went all of the way to the Supreme Court of Canada.
The total value of the service and support agreement is $1.5 billion, if every extension is exercised.
Critics have said Canada could have purchased a couple of brand new submarines for that price tag.
Associate defence minister Kerry-Lynne Findlay said the latest extension is an important investment in the country's marine sector and will support more than 400 high-quality, skilled jobs across Canada.
Note to readers: This is a corrected story. An earlier version misspelled Kerry-Lynne Findlay's first name.