The owner of Devonport Dockyard in Plymouth has been guaranteed 15 years of work as a preferred engineering supplier for warships and submarines.
Some of Babcock's work will be carried out at Devonport Dockyard
Babcock International confirmed that it would be guaranteed the work between 2010 and 2025 after signing a terms of business agreement with the MoD.
The deal, worth about £1.2bn, is for the provision of submarine support, maintenance and decommissioning.
The work will be carried out at Devonport and on Clydeside, Scotland.
Defence Secretary Bob Ainsworth said the company would be Britain's lead partner for submarine work and the agreement would deliver savings and benefits to the MoD.