Receiver Eric Saubert made the decisive two-point conversion for Seattle.
Seattle engineered a stunning fightback to overcome the Los Angeles Rams in overtime, securing their spot in the NFL play-offs.
Rallying from a 30-14 hole in the final period, the Seattle squad emerged victorious 38-37 at home, registering their fifth straight victory.
While the Los Angeles had become the first to earn a playoff spot earlier on Sunday, the Seahawks secured their place to the play-offs after a two-year hiatus.
With this outcome, the Seahawks have taken over their Conference race with a twelve and three record, replacing the Rams, who dropped to the number five playoff position with an 11-4 record.
Quarterback Darnold threw two interceptions but recovered to deliver two touchdown passes, including the second TD to wideout Jaxon Smith-Njigba in overtime.
The Rams held a 13-7 lead at half-time before Walker broke free for a 55-yard scoring dash for the home side.
Los Angeles cornerback Josh Wallace then returned Darnold's initial pick for a big return, setting up a short score by Blake Corum on the ensuing snap.
In the final stanza, a touchdown from Matthew Stafford to Nacua pushed the Rams' lead to sixteen points, but Rashid Shaheed provided the comeback with a spectacular punt return.
Darnold then found AJ Barner in the end zone, and a successful two-point play sent the contest into an extra period.
Although Puka Nacua scored for his second TD in overtime, Smith-Njigba answered in kind to set up the decisive conversion.
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