"Thomas provides a veteran in the secondary who is familiar with the NFC South and has been a very solid player," coach Ron Rivera said. "We are pleased to add him to a safety group that has good experience and production."
He visited the Panthers this week.
He previously visited the Detroit Lions.
DeCoud was a Pro Bowl selection in 2012, but was due a $4.2 million base salary in 2014 and was released.
The Falcons saved $3 million in salary-cap space by cutting DeCoud.
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Aaron Wilson covers the Ravens for The Baltimore Sun