Sources told ESPN's Adam Schefter it is a five-year, $98.5 million extension that will make Leonard the highest-paid inside linebacker in NFL history.
"I'm a competitor. If you're not first, you're last," Leonard said of besting Warner's deal. "To have my name at the top, that's something I don't take for granted. I have to continue to go out and prove that. You've seen the [linebacker] rankings; I think I was sixth, I was No. 8 on Madden."
Leonard joins offensive tackle Braden Smith as the two players the Colts have locked up to long-term extensions during training camp.
Leonard said he hopes to make his training camp debut this week after offseason ankle surgery.
The 26-year-old Leonard was a first-team All-Pro for the second time in 2020, when he had 132 tackles, three sacks, three forced fumbles and two fumble recoveries while helping the Colts return to the playoffs after a one-year absence. He was the Defensive Rookie of the Year in 2018, when he led the NFL with 163 tackles and also recorded seven sacks.
A second-round draft selection in 2018, Leonard has 416 tackles in three seasons and also has 15 career sacks and seven interceptions.
"We all know Darius, that chip has served him well," coach Frank Reich said. "Whatever level of disrespect he felt from all that, he's used that as a motivator in [his] own way, but what I've learned to appreciate about Darius is he's going to be motivated no matter what to be the very best. He's going to hold himself to those standards."
ESPN's Mike Wells contributed to this report.