Cockatoo Dockyard began a long involvement with the refit and repair of submarines with the docking of the RAN submarines AE1 and AE2 in 1914. Refits of the J class followed in the early 1920s, and the RAN’s Oxley and Otway came to the island in 1929–31.

Many submarines came to the island for docking between 1945 and 1960, when refits began of the Royal Navy T-class submarines of the 4th Submarine Division based in Sydney. The last of these five refits completed in 1966. The work provided excellent training for the workforce in preparation for the refits of the RAN’s Oberon-class submarines which began in 1971.

Cockatoo Dockyard completed 14 major refits of these submarines, including a major modernisation programme. In addition, 15 mid-cycle survey dockings, 39 intermediate dockings and 14 unprogrammed dockings were successfully completed at the dockyard. The last refit, of HMAS Orion, was completed on 4 June 1991, ending the long history of support for the RAN by Cockatoo Dockyard.