A new "world-class museum resource" for maritime, military and science exhibits is due to open in 2010 after funding for the project rose to nearly £10m.
Our Maritime World gallery will tell the story of a 1920s passenger liner
National Museums at Chatham, located in the Thames Gateway area of Kent, is a partnership between three museums and Chatham Historic Dockyard Trust.
It will house 5,000 artefacts and model ships, as well as offering education spaces and temporary exhibitions.
The Prince of Wales has agreed to be the patron for the project.
The Dockyard Trust, based in Chatham, is working with the National Maritime Museum, the Imperial War Museum and the Science Museum.
The 198-year-old No 1 Smithery building was on an "at risk" register
Funding has come from the Heritage Lottery Fund (£4.97m) and the South East England Development Agency (£2m).
Another £2.2m is going towards a major restoration of the No 1 Smithery building at the dockyard, which will be home to the National Museums' collections.
The total cost of the project is estimated at £14m.
The museums involved will transfer exhibits to the refurbished buildings, from where they will be available for public viewing or research purposes.
"Access to collections is the key ethos of all museums," said Roy Clare, director of the National Maritime Museum.
The public galleries being developed for National Museums at Chatham include one called Treasures, to house maritime exhibits and supporting artworks and archives.