According to a source, the Colts are giving Gilmore a two-year, $23 million contract that includes 14 million guaranteed.
Gilmore is the second veteran to join the Colts' secondary this week.
Gilmore was traded to the New England Pats in October for a third-round pick. Jaycee Horn, the first-round pick of the Carolinas, suffered a season-ending foot injury in the third game of the season.
Gilmore was on the physically unable to perform list when he arrived in Carolina, still recovering from surgery on his quad and not eligible to return until Week 6. He played the final eight games after being activated in Week 8. He had an intercept in his Carolina debut at Atlanta to preserve a 19-13 victory and then another in his home debut against New England. He was added to the Pro Bowl as an alternate.
He did not like the way New England dealt with his quad injury in Week 15 of the 2020 season.
Gilmore said before the Buffalo game that he would like to return to Carolina. The veteran leadership brought to the Carolina secondary was liked by the panthers. Donte Jackson, the second-round pick who re-signed with the Panthers last month, was complicating the issue.
Gilmore was the 10th overall pick in the 2012 draft by the Bills.
DavidNewton contributed to the report.