Larry Fitzgerald made a pair of key catches in the Cardinals' final possession, including a 26-yard grab on third-and-3 that put Arizona (8-8) at the Seattle 48-yard-line.
His subsequent 12-yard reception from John Skelton on a one-handed grab got the ball closer and set up Feely's game-winning field goal.
The Cardinals receiver finished with nine catches for 149 yards. Skelton tossed for 271 yards, one touchdown and one interception on 22-of-40 efficiency.
Arizona wrapped up the season with seven wins in nine games, including four in extra time.
Seattle (7-9) was led by Tarvaris Jackson, who went 21-of-35 through the air 222 yards, one score and one interception.