The refit of HMCS Victoria will continue until 2011, Defence officials said Thursday.
The submarine, which has been in dry dock at CFB Esquimalt near Victoria for more than three years, was expected to return to service in late 2010.
Prior to that, it had been expected to return to service in late 2009.
A lack of parts and technical knowledge were blamed for the delays, the Defence department said.
Three other submarines are also being refitted. The Defence department said the lessons learned from the Victoria refit are being applied to those, one of which, HMCS Chicoutimi, suffered a fire that killed one sailor during its maiden voyage in 2004.
The Chicoutimi is not expected to be back in service until 2012.
Canada bought the four submarines from Britain in 1998; the controversial deal was worth hundreds of millions of dollars.