Tight end Eric Saubert executed the game-winning two-point conversion for Seattle.
Seattle engineered a remarkable comeback to defeat the Los Angeles Rams in overtime, clinching their place in the NFL play-offs.
Overcoming a 30-14 hole in the final period, the Seahawks triumphed 38-37 at home, notching their fifth consecutive victory.
While the Rams had already secured a post-season spot earlier on game day, the Seattle team booked their return to the play-offs after a two-year hiatus.
With this result, the Seattle have taken over their division's race with a twelve and three record, replacing the Rams, who dropped to the fifth seed with an 11-4 record.
Signal-caller Darnold had two picks but recovered to deliver two touchdown passes, culminating in the second TD to wideout Smith-Njigba in the extra period.
The Rams held a 13-7 advantage at the break before Walker broke free for a long scoring dash for Seattle.
Los Angeles defensive back Wallace then returned Darnold's first pick for a big return, setting up a one-yard score by Blake Corum on the next play.
In the final stanza, a touchdown from Stafford to Puka Nacua pushed the Rams' lead to sixteen points, but Rashid Shaheed ignited Seattle's hope with a 58-yard punt return.
Darnold then found AJ Barner in the end zone, and a successful conversion forced the contest into overtime.
Although Puka Nacua raced in for his another TD in overtime, Jaxon Smith-Njigba responded in kind to setup the decisive conversion.