Just a few days after the NFL's sixth regular-season game at Wembley Stadium, Johnson said he has spoken with the league about playing more games in the British capital.
"Sunday's game at Wembley, in front of over 80,000 fans, further cements London's reputation as the natural home of American football outside of the United States," the mayor's office said in a statement.
"Given the ever growing popularity of gridiron on this side of the Atlantic, the mayor and his team have held a number of meetings with senior executives in the last few days to explore further opportunities involving the NFL and London. The talks were exploratory. We are at an early stage, but the signs are encouraging."
All six NFL games in London so far have been at Wembley, including the New England Patriots' 45-7 win over the St. Louis Rams on Sunday. The two games scheduled for next season are also set for Wembley, and the NFL has a contract with Wembley through 2016.
But the Olympic Stadium, built for this year's games, have yet to find a permanent resident. Johnson happens to be the chairman of the London Legacy Development Corporation, which is responsible for deciding how the Olympic Stadium will be used in the future.
A decision on the future of the stadium is not expected before December. West Ham, a London soccer team, is the leading contender to take up residency—and keep the running track in place.
The Olympic Stadium is not due to reopen before 2014.
The NFL said it has been in talks with local authorities in London for years about future possibilities.
The Jacksonville Jaguars have a deal to play one home game in London for four consecutive seasons, beginning in 2013. The NFL has raised the possibility of having a full-time franchise in London, although that is still considered a long shot.