Creative Taste, from caterer Creativevents, has reported a 60% increase in public catering revenue since its June re-launch of the Dulwich Picture Gallery Café.
The news comes just months after the firm won a £3.8m hospitality contract with the venue.
Open all day, the Picture Gallery Café has been completely renovated, and offers breakfast, brunch, lunch and afternoon tea, plus roasts at the weekend. It also has a children's menu with smaller plates of the adult choices.
The site is also available to hire for private evening occasions.
Creativevents' business development director, Zoë Watts, said: "Our mission at Creative Taste is to add innovation to catering in public spaces. We have enjoyed a great summer at Dulwich already."
The company has also confirmed that it is looking to help expand the Gallery's wedding and corporate business over the next year.
The Dulwich Picture Gallery Café was Creative Taste's first contract win after a majority stake in Creativevents was bought by facilities management company Mitie last August.