Palmer twice was intercepted in the end zone, including Richard Sherman's second pick of the game early in the fourth quarter. After Seattle (12-3) took a 10-9 lead with 7:26 left, Palmer led the Cardinals 75 yards and found Floyd for a juggling TD catch with 2:13 left.
Arizona wrapped up the stunning victory when Wilson's pass deflected off Doug Baldwin's arm and was intercepted by Karlos Dansby with 1:56 left. The Cardinals were able to celebrate handing Seattle its first home loss since Dec. 24, 2011 against San Francisco and the first for Wilson.
Palmer finished 13 of 25 for 178 yards. Floyd's TD reception was his only catch and Larry Fitzgerald was held to three catches for 18 yards.
It was the second time in three weeks the Seahawks let a fourth-quarter lead slip away.
Despite those paltry numbers and Palmer's interceptions, the Cardinals had a chance late because of their defense.
Wilson finished 11 of 27 for 108 yards, taking his first home loss since he was at North Carolina State. He rarely had time to throw and when he did, he missed open receivers. His final pass was underthrown, with Doug Baldwin wide open if the throw was on target.
Palmer's winning drive made up for his earlier errors. He was intercepted in the end zone first by Kam Chancellor on Arizona's opening drive. He was picked off by Malcolm Smith in Seattle territory in the second quarter, and twice threw interceptions into Sherman's arms.
But Palmer was fantastic on Arizona's decisive drive. It started with a third-down completion as he was about to get sandwiched by Clinton McDonald, flipping a pass to Jake Ballard for 17 yards. The drive was kept going when Smith was flagged for defensive holding on a third-down incompletion.
On third-and-6, Palmer dropped a perfect throw beyond cornerback Byron Maxwell and into Floyd's hands. He juggled it at first but controlled the ball as he hit the turf.
Rashard Mendenhall scored easily on the 2-point conversion with 2:13 left.
The Seahawks finally took the lead on Zach Miller's 11-yard TD catch. The extra point was blocked, but the Cardinals were flagged for an illegal formation. Steven Hauschka converted the second attempt.
To that point, the Seahawks went three-and-out seven times. Wilson was sacked four times. Marshawn Lynch rushed for 71 yards, but Seattle had just 22:36 time of possession.
Seattle also failed to capitalize at the end of the first half when Smith returned Palmer's interception to the Arizona 3. Lynch was stopped on two runs and Hauschka's 24-yard field goal hit the left upright following a high snap. It snapped a streak of 22 straight makes for Hauschka.
AP NFL website: www.pro32.ap.org