The 49ers will be listed as the home team for the Oct. 31 game.
"For the past three years we have seen the extraordinary passion that exists for NFL football in the U.K.," NFL commissioner Roger Goodell said in a statement. "We want to continue to build on that passion by strengthening our ties to our existing U.K. fans and creating new ones."
The game between the five-time Super Bowl champion 49ers and two-time champion Broncos may not be the only one in Britain next season.
"The NFL will continue to explore the possibility of playing a second game in the U.K. in 2010," the NFL said.
The 49ers and Broncos struggled to 8-8 records this season and missed the playoffs.
The NFL has played games at Wembley for the last three seasons, with more than 80,000 fans at each game. The first game featured the eventual Super Bowl champion New York Giants beating the Miami Dolphins 13-10. In 2008, the New Orleans Saints beat the San Diego Chargers 37-32. And this season, the New England Patriots defeated the Tampa Bay Buccaneers 35-7 in October.
"The previous games in London have had a playoff-like atmosphere to them, so that's always a good thing to play in that type of an environment," Broncos coach Josh McDaniels said. "We'll be ready for the challenge."
The 49ers dominated the NFL in the 1980s, winning four Super Bowls with Joe Montana as the star quarterback. The team won another Super Bowl in 1994.
"London is a wonderful venue for two of the most storied franchises in NFL history to square off," 49ers president Jed York said.
San Francisco coach Mike Singletary, who is giving up a home game to play in London, said his players won't be bothered by the long flight to England.
"I have no doubt that our players will be ready to go," he said. "What a great opportunity it is for us to play in such a setting."
The Broncos have played seven international exhibition games in the past, and team president Pat Bowlen said they were "honored" to come to Britain again.
"It's a wonderful, historic opportunity for our franchise and will be an unforgettable experience for our players, coaches and fans," Bowlen said.
Aside from Wembley, Manchester and Glasgow, Scotland, are being looked at as potential venues to host NFL games.
In October, before the New England-Tampa Bay game, Goodell said the idea of eventually putting an expansion team in London was of "tremendous interest" to the NFL. He gave no timeline when such a decision might be taken.