BaxterStorey has scooped a £5.2m catering deal with the National Archives in Kew, south east London.
The contract starts in July this year and runs for five years, with the option to extend for two extra years.
BaxterStorey will takeover from the present catering firm, Genuine Dining Co, which has worked at the site since 2007.
The catering team will operate the main restaurant, coffee bar, and staff canteen.
The National Archive, which holds over 11 million historical and government records, has around 550 staff, and sees 80,000 visitors each year.
There are plans to redevelop its public space with aims to increase the annual visitor numbers to 180,000 within the next six year.