eahawks quarterback Russell Wilson picked out Doug Baldwin for a 29-yard touchdown and then connected with Jimmy Graham...
Walsh could have taken the game to overtime with seven seconds left on the clock but his potentially game-tying field goal from 52 yards dropped just short of the bar as Atlanta escaped.
The Falcons had looked to be heading for a straightforward win after quarterback Matt Ryan threw two touchdown passes to help put the Falcons 11 points clear in the fourth quarter.
But Seahawks quarterback Russell Wilson picked out Doug Baldwin for a 29-yard touchdown and then connected with Jimmy Graham for a two-point conversion to put Seattle within a field goal of tying the game.
Atlanta needed one first down to run out the clock but Ryan was sacked as the Seahawks regained possession to mount one last drive.
But after marching upfield to put Walsh in range, the Seahawks kicker was unable to deliver.
It was another cruel blow for Walsh, who joined Seattle from Minnesota in the close season. Walsh has already cost his team one victory this season, missing three kicks in a 17-14 defeat to the Washington Redskins earlier this month.
The Atlanta win continues the Falcons' revival after a convincing rout of Dallas last week. Atlanta, last season's Super Bowl runners-up, improved to 6-4 with the win and are now in the hunt for a playoff berth.
Seattle however fell to 6-4 with the defeat, missing the chance to go level with the Los Angeles Rams (7-3) at the top of the NFC West.
Atlanta are now two games behind the New Orleans Saints in the NFC South but the victory could be significant in the playoff chase. Atlanta would edge out Seattle on head-to-head record if any tiebreaker for a postseason spot was necessary.
Ryan meanwhile made 19 of 27 passes for 195 yards while Seahawks star Wilson threw for 258 yards with two touchdown passes and one interception.