Welker leaves Foxborough after contract talks with the Patriots stalled, agreeing a contract in Denver reported to be worth 12million US dollars.
Welker struck up a potent partnership with three-time Super Bowl-winning quarterback Tom Brady after joining the Pats in 2007, recording 100-catch, 1,000-yard seasons in five of the last six years.
The five-time Pro Bowl receiver will now become a primary target for another legendary NFL quarterback in Peyton Manning, who is coming off the back of a successful first season with the Broncos after leaving Indianapolis.
"Excited to have Wes join the Broncos," Denver's executive vice-president of football operations John Elway said on Twitter.
"His production and toughness will be a great asset!"
Welker joins Demaryius Thomas and Eric Decker in a potent receiving line-up in Denver, after all three men racked up at least 1,000 yards on receptions in 2012.