Rams quarterback Jared Goff, who underwent surgery on his right thumb less than two weeks ago, was forced into action after starter John Wolford was transported to the hospital following a neck injury.
In place of Wolford, Goff completed 9 of 19 passes for 155 yards. He capped the victory with a 15-yard touchdown pass to receiver Robert Woods with 4:46 remaining in the game.
"We come up here, and all week we were told how good they are and how we snuck into the playoffs," Goff said. "Two weeks ago you saw them smoking cigars and getting all excited about beating us and winning the division, and we were able to come up here and beat them."
Rams rookie running back Cam Akers rushed for 131 yards and a touchdown in his postseason debut. Cooper Kupp led the team with 78 receiving yards on four receptions.
Midway through the second quarter, Los Angeles defensive back Darious Williams picked off Seahawks quarterback Russell Wilson and returned it 42 yards for a touchdown as the Rams defense continually pressured the Pro Bowl signal-caller.
The Rams totaled five sacks and allowed only 278 total yards. Seattle had just 11 first downs in the game.
"A lot of guys stepped up and answered the bell in a big way," Rams head coach Sean McVay said. "Darious Williams showing up, I thought that was a huge momentum shift for us."
Wilson completed 11 of 27 passes for 174 yards and two touchdowns. He added four carries for 50 yards.
"We're excited about competing to go see who we play next and see if we can keep this thing rolling," McVay said. "But we'll enjoy this."