Stewart was drafted by the Indianapolis Colts in the fourth round, 144th overall, in the 2017 NFL draft.[4] As a rookie, he finished with 23 total tackles (12 solo) in 14 games.[5]
After being a backup in his first two seasons, Stewart became a full-time starter in 2019. He had his first career sack in Week 2 of 2019. He finished the season playing in all 16 games with 13 starts, recording three sacks, 30 tackles and a pass deflection.[6]
On November 28, 2020, Stewart signed a three-year, $30.75 million contract extension through the 2023 season.[7]
On October 17, 2023, Stewart was suspended six games for violating the NFL policy on performance-enhancing drugs.[8] He finished the season with 41 tackles and 0.5 sacks through 11 starts.[9]
On March 11, 2024, the Colts signed Stewart to a three-year, $39 million contract extension.[10]