The couple were spotted at Byron Hamburgers in Kensington.
“They were having a good time,” a source at the eatery tells PEOPLE.
Staff at the burger joint would not say what the couple ate, but Harry is apparently a regular visitor at Byron, which is just a short drive from his apartment at Kensington Palace.
A British newspaper report recently claimed that Harry, 29, and Cressida, 24, were heading for a split because they had not been spending much time together since his return from his trek for charity across the ice of Antarctica.
But the couple have been seeing each other privately – and quietly – at the country homes of friends.