Rower Alex Partridge and field hockey player Hannah Macleod issued public appeals for the return of the medals, which they earned during the 2012 London Olympics. The thefts reportedly occurred at the Mahiki nightclub, where the athletes went following a reception at Buckingham Palace hosted by Queen Elizabeth II in honour of Britain's Olympic team.
"I'm absolutely gutted that my Olympic bronze medal has been stolen," Macleod said in a statement. "Winning it in August was an incredible highlight for me, and for this to have happened is simply shattering."
Macleod was a member of the women's team that defeated New Zealand, 3-1.
"While it means everything to me, it has no value to anyone else, and I just hope that whoever took it can hand it in or leave it somewhere that means I can get it back," she said.
Partridge, a member of the men's eight rowing team, said his team blazer was also taken.
The jacket was later handed in at a northwest London police station, but not the medal, according to police.
Police investigating the alleged theft of the medals said a 31-year-old man had been arrested and was later released on bail.