Buckner tested positive for the coronavirus last week and missed the Colts' pivotal AFC South matchup against the Tennessee Titans as a result.
The interior rusher is now eligible to play in Week 13 versus the Houston Texans.
Buckner, 26, is in the midst of a strong campaign and should be in contention for All-Pro honors. He's amassed 41 tackles, 2.5 sacks, one forced fumble, and a fumble recovery through 10 games in 2020.
Indianapolis was also missing versatile lineman Denico Autry last week after he was deemed a close contact, but the team activated him from the COVID-19 list Thursday.
The Colts sit second in the AFC South at 7-4 and currently occupy the conference's final wild-card spot.