The Panthers made roster room for Thomas by waiving reserve offensive lineman Tim Duckworth.
Thomas was the Redskins' second-round draft pick in 2008 and has caught 40 passes for 446 yards and three touchdowns in his NFL career. But he failed to impress new Redskins coach Mike Shanahan and was dogged with questions about his work ethic.
Washington waived Thomas on Saturday, and Shanahan contended that the receiver's professionalism was lacking.
"Everybody's got a different mindset on what work means, what dedication means, what commitment means," the coach said Monday. "All I told Devin was if you want to be the best player you want to be, your commitment is going to have to be stronger."
The Indianapolis Colts also placed a waiver claim on Thomas, a league source told NFL Network insider Jason La Canfora.
The Associated Press contributed to this report.