Brackett had been limited to one practice per day because of an offseason hip injury until last Thursday when he went down with what was initially called a hip injury and then changed to a groin injury on the team's weekend injury report.
It was a welcome addition for a linebacking corps that has been short-handed since Indianapolis first practiced July 25. Another starter, Tyjuan Hagler, is expected to be out until October after tearing a pectoral muscle while lifting weights in the offseason.
"Yes, Gary's back and it's good to have him back," coach Tony Dungy said.
Dungy did not say whether Brackett would play Saturday at Carolina.
The Colts also added another linebacker to the roster, signing former Washington linebacker Danny Verdun-Wheeler. Brandon Archer was placed on the waived-injured list. Archer played last season with the Colts and was re-signed last week.
"He played against us the other night, and we liked what we saw, so we thought we'd take a look at him," Dungy said of Verdun-Wheeler.
The Colts' injuries have continued to pile up, though.
Two-time league MVP Peyton Manning, 2007 Defensive Player of the Year Bob Sanders, former league sacks champion Dwight Freeney, starting guard Ryan Lilja, rookie tight end Tom Santi and Hagler remain on the physically unable to perform list.
Offensive tackle Corey Hilliard wore a walking boot to Thursday night's workout after getting hurt in the morning practice and receiver Onrea Jones, who caught a touchdown pass in Sunday's 30-16 loss to the Redskins, strained a hamstring.
And Indy has likely lost defensive back Michael Coe for up to eight weeks after he had knee surgery.