Jaxon Smith-Njigba had seven catches for 92 yards and two touchdowns for Seattle (10-3), which outscored the Falcons 31-3 in the second half.
Kirk Cousins completed just 15 of 30 passes for 162 yards and two interceptions. Bijan Robinson rushed for 86 yards for the reeling Falcons (4-9), who secured their eighth straight losing season.
Seattle scored the game’s first touchdown on the opening play of the second half, as Rashid Shaheed’s 100-yard kickoff return gave the Seahawks a 13-6 lead.
Atlanta threatened on its ensuing drive, but Robinson’s fumble was recovered by Devon Witherspoon at Seattle’s 12-yard line with 11:18 left in the third.
On the Seahawks’ next drive, Darnold completed each of his five passes for 80 yards, including a 28-yard touchdown to Smith-Njigba to give the visitors a 20-6 lead.
The Falcons continued to unravel as Cousins’ pass skipped off Kyle Pitts’ hands and was intercepted by Nick Emmanwori at Atlanta’s 47.
The Seahawks tacked on Jason Myers’ 37-yard field goal at the 2:39 mark of the third before Zane Gonzalez’s 27-yard field goal cut Atlanta’s deficit to 23-9 on the first play of the fourth.
Darnold hit Cooper Kupp for an 11-yard touchdown pass to push the lead to 21 with 12:13 left.
Witherspoon picked off Cousins in Falcons territory and Smith-Njigba hauled in his second score, this one a 4-yarder to give Seattle a 37-9 advantage with 8:27 remaining.
After James Pearce Jr. sacked Darnold to force Seattle’s punt on its opening drive, Atlanta struck first on Gonzalez’s 35-yard field goal with 7:14 left in the first quarter.
Seattle answered with a 12-play, 70-yard drive that set up Myers’ game-tying 22-yarder.
Following Atlanta’s second punt, Mike Hughes intercepted Darnold and returned it six yards to Seattle’s 30-yard line. The Falcons couldn’t capitalize on the turnover, as they were forced to settle for Gonzalez’s 50-yard field goal attempt, which was blocked by Emmanwori.
After another Seattle punt, the Falcons doubled their lead on Gonzalez’s 43-yard field goal with 1:01 left in the first half.
The Seahawks pulled even at 6-6 at halftime, as Myers drilled a 48-yarder as time expired.
