The defensive tackle has not played in the NFL since featuring for the Seattle Seahawks in the 2010 campaign.
The 33-year-old told the Panthers' website: "It's going good. I'm continuing to work, improve and knock the rust off. I'm just going to continue to max out my reps every chance I get and work as hard as I can to help this team.
Head coach Ron Rivera added: "I'm pretty excited about him. He's got an opportunity to come back, and he's a big, stout physical guy that you have a place for, but we'll really see as we start playing games."
Cole was released from his contract with the Seahawks after sustaining an ankle injury.