Second-seeded Houston, seeking its third MLS title in four seasons, denied a frantic late flurry of corner kicks and set plays by Sounders star Freddie Ljungberg.
The playoff opener was yet another splashy event in the Sounders' smashing inaugural season.
Seattle, the third seed in the Western Conference, set attendance records while becoming the first expansion team in 11 years to reach the MLS postseason.
The crowd of 35,807 at Qwest Field was the largest crowd for a conference semifinal playoff match in MLS' 13-year history.
It was the fourth scoreless draw this season for each team.
The second match of the series is Nov. 8 at Houston, where the Dynamo are 4-1 in the playoffs. They also have the league's best home winning percentage over the last four seasons. The winner advances to the one-match conference championship.
Houston could use the 10-day break after playing four times in 12 days.
Most of the rowdy fans were standing, singing and chanting and waving signs such as "Welcome to Green Hell" throughout the chilly night.
Lead owner and Hollywood filmmaker Joe Roth attended, and minority team owner actor Drew Carey walked the perimeter of the field before the game wearing a huge smile, a white team cap and one of the green-and-blue team scarves that were everywhere in the stadium and atop freeway overpasses around the city
The two stingiest defenses during the regular season -- 29 goals against each in 30 games -- bulled through 60 minutes. There were only two prime scoring chances in that span. The first came from former Dynamo player Patrick Ianni, who started because Tyrone Marshall had a sprained knee. He headed a shot off the crossbar in the 43rd minute on long free kick by Ljungberg.
In the 58th minute, Houston All-Star midfielder Brad Davis had his shot from the top of the penalty area poked away with a right hand by diving goalkeeper Kasey Keller.
The chippiness started when Houston goalkeeper Pat Onstad bulled Fredy Montero, Seattle's top scorer, to the ground in front of the goal after a whistle in the 16th minute. Onstad received a yellow card, as did Montero for racing up off the turf and charging at his 41-year-old opponent.
Ljungberg, who missed on numerous passes early in his first MLS playoff game, had pointed words for Onstad at the end of the skirmish. Houston's Brian Mullan yanking Seattle's Jhon Kennedy Hurtado away from the scrum with his arm around Hurtado's neck.
The raucous crowd lustily booed Onstad each time he touched the ball after that.
Eleven minutes later, Houston's Ricardo Clark kicked former Dynamo forward Nate Jaqua above his left eye. Jaqua left the pitch for 3 minutes of game time after blood trickled down his face, but Houston couldn't muster a scoring chance with the brief man advantage.
The cut and blood bothered Jaqua into the second half, when the most impressive player in the match finally summoned trainers to wrap the circumference of his head. Seattle's 2008 expansion draft pick from Houston also had to change his bloodstained jersey, into one with no name or number on the back.
Jaqua returned again to poke a short pass in front for Montero in the 61st minute. Montero, who had 12 goals in the regular season, dribbled his point-blank shot just outside of the right post.
Jaqua was turned away by Onstad on a header from close-range, off a corner kick by Ljungberg in the 74th minute.
Houston................0 0--0At Seattle FC .................0 0--0
• First half: None.• Second half: None.• Goalies: Houston, Pat Onstad; Seattle FC, Kasey Keller.• Yellow Cards: Montero, Seattle FC, 16th; Onstad, Houston, 16th; Alonso, Seattle FC, 64th; Evans, Seattle FC, 68th; Mullan, Houston, 71st; Chabala, Houston, 75th.• Referee: Ricardo Salazar. Assistant Referees--Steve Taylor. Hector Vergara. 4th Official--Edvin Jurisevic.• A: 35,807
• Houston: Pat Onstad, Brian Ching (Cam Weaver, 89th), Brad Davis, Ricardo Clark, Geoff Cameron, Dominic Oduro (Luis Angel Landin, 79th), Mike Chabala, Stuart Holden, Andrew Hainault, Brian Mullan, Bobby Boswell.
• Seattle FC: Kasey Keller, Patrick Ianni, Freddie Ljungberg, Fredy Montero (Roger Levesque, 63rd), Steve Zakuani (Sebastien Le Toux, 82nd), Brad Evans, Osvaldo Alonso, Nate Jaqua, Jhon Kennedy Hurtado, James Riley, Leo Gonzalez.