Gruden will join play-by-play announcer Mike Tirico and former NFL quarterback Ron Jaworski.
"This is a tremendous opportunity and I am very excited to be associated with ESPN and Monday Night Football," Gruden said in a statement released by ESPN. "I grew up a fan of Monday Night Football and whether I've coached on Monday night or watched, I've hardly missed a game all these years."
Gruden was fired in January after coaching the Buccaneers for seven seasons. He also coached the Oakland Raiders for four years and has an overall coaching record of 95-81.
Kornheiser, who appears on ESPN's "Pardon the Interruption," often rode a bus to get to games the last three seasons but said this year's schedule would make that difficult.
"My fear of planes is legendary and sadly true," he said on ESPN.com. "When I looked at the upcoming schedule it was the perfect storm that would've frequently moved me from the bus to the air. I kept looking at the schedule the past month and wanted to find a way to quietly extricate myself."
"Monday Night Football" marks its 40th season in 2009 with two games on Sept. 14: Buffalo at New England and San Diego at Oakland.