The Chiefs insisted they also improved their chances for success in 2009 by making the trade.
The Falcons will send a second-round pick in 2010 to Kansas City in exchange for Gonzalez, the only tight end in NFL history selected to 10 Pro Bowls.
Gonzalez caught 96 passes for 1,058 yards and 10 touchdowns in 2008. He owns NFL career records for tight ends with 916 receptions, 10,940 yards receiving, 76 TDs receiving and 26 100-yard receiving games.
One of the most popular athletes Kansas City has ever had in any sport, Gonzalez said leaving the town and its fans is not easy.
"I love Kansas City," he said in an interview with The Associated Press. "The fans have been unbelievable to me. I'm going to miss them. This is a happy day for me, but in many ways it's a sad day, too. I'm going to miss running out that tunnel and seeing that sea of red in those stands."
General manager Scott Pioli said the Chiefs, 2-14 in 2008, did not pursue a trade for Gonzalez, but they agreed when the Falcons offered a second-round pick.
Gonzalez will provide a dramatic new look for the Falcons, who were 11-5 last year with rookie quarterback Matt Ryan starting every game.
"Tony's arrival will make an instant impact not only on the offensive side of the ball, but on the overall team in general," said Ryan, the NFL Offensive Rookie of the Year. "I feel privileged to be throwing the ball to a future Hall of Famer and I'm anxious to get on the field to start working with him."
The 33-year-old Gonzalez, who has three years remaining on his contract, asked to be traded last October. The trade addresses one of the Falcons' top needs, freeing the organization to make defense the top priority in this weekend's draft.
The Falcons expect to receive compensatory picks next year for losing several free agents, including cornerback Domonique Foxworth and linebackers Michael Boley and Keith Brooking.
Gonzalez will join Pro Bowl receiver Roddy White to give the Falcons more passing balance.
"Anybody would be excited to be a part of that offense," Gonzalez said. "With Michael Turner, Matt Ryan and the other guys, we have a chance to be in the top five in the league in offense."
UPGRADE ON OFFENSE
The Falcons bolstered their offense with the acquisition of Tony Gonzalez. A look at the 10-time Pro Bowl tight end's numbers with the Chiefs and the three players Atlanta used at the position last season: