The result means Real Salt Lake, which finished the season with 57 points, will enter the Western Conference playoffs as the No. 2 seed.
Seattle, which ended up with 56 points, is the third seed.
"We know we have a big challenge ahead of us," RSL midfielder Kyle Beckerman said. "But we feel confident. We feel like we have every right and every opportunity to go ahead in the tournament."
Real Salt Lake comes off a 0-0 draw against Vancouver on Saturday night.
It was RSL's third straight match without a goal, although nobody seems overly concerned heading into the postseason.
Coach Jason Kreis joked after the game that his team had stored some goals "in the bank" and would retrieve them when the playoffs started.
RSL will count on a spark from forwards Alvaro Saborio and Fabian Espindola, who scored 26 of Real Salt Lake's 46 goals during the regular season.
"I know the guys can score," Beckerman said. "I know they are trying. Maybe they are thinking too much. Sometimes that happens. But [they] have plenty of goals to come. We'll be counting on them to get some for us."
Real Salt Lake should be relatively healthy for the playoffs.
Keeper Nick Rimando (shoulder), defender Nat Borchers (quad) and defender Jamison Olave (hamstring) sat out the match against Vancouver as a precaution.
Javier Morales did not play because of the flu.
Meanwhile, midfielder Ned Grabavoy (quad) and defender Kwame Watson-Siriboe (leg strain) returned after month-long absences. They played deep into the second half.
Real Salt Lake is 1-0-2 against Seattle this season.
Espindola's goal in the 50th minutes gave RSL a 1-0 victory on May 12 at Rio Tinto.
In the rematch, Real Salt Lake was held to a 0-0 draw at CenturyLink Field on Oct. 17 despite having a one-man advantage for the final 60 minutes.
RSL playoff schedule
The schedule for Real Salt Lake's two-game aggregate playoff series against Seattle:
P Game 1 • Friday
RSL at Seattle
Game 2 • Nov. 8
Seattle at RSL