Cole improved to 16-5, his 12th straight win matching a club record set in 1993 by Mark Portugal and equalled in 2002 by Wade Miller.
He retired 24 of 25 batters he faced, with a home run by Seattle's Shed Long the only hit he surrendered all day.
Meanwhile the Astros offense pummelled Mariners pitcher Felix Hernandez.
Hernandez allowed 11 runs, seven earned, in less than three innings.
He gave up four runs in the second and surrendered six doubles a walk and a hit batter in the third when the Astros erupted for nine runs.
The Astros took their season record against Seattle to 16-1.
Once Hernandez departed after facing seven batters without getting an out in the third inning, the Astros unloaded on the Mariners bullpen scoring three runs in two innings against relief pitcher Wade LeBlanc and five off Reggie McClain in the seventh.