The deal links Kelce and the Chiefs through 2021.
"I just want to say thank you to everyone from the top of the list to the bottom," Kelce said Friday on a conference call. "[Team CEO and chairman] Clark Hunt, coach Andy Reid, all the coaching staff that's with me, John Dorsey, these guys believed in me enough when I got drafted and obviously still are behind me every step of the way. I can't thank them enough, I can't thank my coaches enough, I can't thank the players that I play with enough."
The Chiefs tweeted Friday that Kelce had signed the extension while in Hawaii for the Pro Bowl. They did not disclose contract terms.
Kelce said one of the first people he heard from to congratulate him was wide receiver Jeremy Maclin.
"Everyone's happy for one another, and it's going to be fun working with him and everybody else in the locker room for years to come," Kelce said.
Kelce has been a consistent target for quarterback Alex Smith over the past two seasons after missing most of his 2013 rookie campaign following knee surgery. Kelce tallied more than 50 receptions and 800 yards in both 2014 and 2015 while catching five touchdown passes each year.
"He's a talented football player that has become an important piece to what we do offensively," Chiefs general manager John Dorsey said in a statement. "Travis is a high-character guy and a leader in our locker room."
Kelce had some character questions coming out of Cincinnati, where he was suspended for an entire season for violating team rules. But not only has Kelce steered clear of trouble with the Chiefs, he has become a locker-room leader and one of the most popular players on the team.
"It's hard to bring all of this to reality," he said. "With all this comes a lot of responsibility, and I'm just more ready than ever to go out here and be a dominant performer for years to come."
Off the field, Kelce is filming his own reality TV dating series. The eight episodes of "Catching Kelce" will run on E! later this year.
Information from The Associated Press contributed to this report.