The three-year deal is worth more than £1.1m in annual turnover and includes DFID's London office in Palace Street.
The contract was previously run by Yes Dining and will see 12 Charlton House staff provide breakfast and lunch services to 1,600 DFID employees at the two sites.
Robyn Jones, chief executive of Charlton House, said: "Our experience of managing prestigious and complex government contracts, such as Her Majesty's Treasury, has helped us to gain this contract."
Charlton House has a turnover of £67m, employs 1,750 people and has 150 contracts.
By Chris Druce
E-mail your comments to Chris Druce here.