Terms of the deal were not announced by DeCoud or the team in public statements released Tuesday.
"Thanks for all the congratulations, everyone," DeCoud told his followers on Twitter. "Looking forward to taking my game to the next level and help the falcons take that next step."
DeCoud has started 47 of his 58 games since the Falcons drafted him in the third round from Cal in 2009. He led Atlanta last season with a career-high four interceptions, ranked third on the team with 109 tackles and finished with seven passed defensed.
Cornerback Brent Grimes, the team leader with 17 passes defensed, has been designated a franchise player, though he wants to sign a long-term deal with Atlanta rather than accept a tender offer worth over $10 million.
Right end John Abraham, who had a team-high 9 1/2 sacks, and middle linebacker Curtis Lofton, are free agents.
The team also announced that reserve tight end Michael Palmer and third-string running back Antone Smith have signed exclusive rights contracts.