Travis Blackley and Jose Veras each pitched a scoreless inning to complete the one-hitter.
It is the third time the Mariners had only one hit in a win. The last time was a 1-0 victory over the Yankees on April 27, 2002.
It was their fewest hits of the season, but they were helped on Saturday by drawing six walks.
Seattle starter Hisashi Iwakuma (9-4) allowed seven hits with two runs and seven strikeouts in seven innings to lower his ERA to 2.99. Tom Wilhelmsen pitched a scoreless ninth for his 21st save.
Bedard yielded three runs — one earned — walked five and struck out a season-high 10. He walked off the field expressionless and was greeted with a standing ovation when he was replaced by Cisnero.
He relied on fastballs between 90-92 mph and mixed in a few curveballs and changeups to keep the Mariners off-balance.
Bedard didn’t allow a baserunner until Kendrys Morales walked to start the fifth inning. But he got back on track after that, retiring the next four batters he faced.
He then issued consecutive walks to Saunders and Brad Miller with one out in the sixth inning. Saunders advanced to third and Miller took second on a passed ball by Jason Castro. Saunders scored on a sacrifice fly by Nick Franklin to get Seattle within 2-1.
A second passed ball by Castro allowed Miller to score and tie it at 2-2.
Raul Ibanez walked before Bedard retired Morales to end the inning.
Bedard retired Kyle Seager on a fly out before he was chased on a walk by Justin Smoak.
Matt Dominguez singled to start the fifth before a double by Jake Elmore. Dominguez scored on a sacrifice fly by Jose Altuve with one out to make it 1-0. A single by Castro sent another run home.
The Astros had runners at second and third with no outs in the third inning, but Iwakuma retired the next three batters, with two strikeouts to end the threat.
Seattle’s tough offensive night ended their franchise-high streak of 23 straight games with a home run. It was their first game without a long ball since June 19.
NOTES: Seager went 0 for 4, to snap a 15-game hitting streak, which was the longest active streak in the majors. … The series wraps up on Sunday when Seattle’s Felix Hernandez (10-4) opposes Jordan Lyles (4-3). Hernandez leads the American League with a 2.53 ERA. … Roger Clemens, the seven-time Cy Young Award winner and special assistant to Houston general manager Jeff Luhnow, was at Minute Maid Park on Saturday. He had a talk with the Astros pitching staff and tried to encourage them to stay positive as the losses continue to pile up.
