The 44-year-old Colon was working on a flawless game for the Texas Rangers before walking Carlos Correa on a 3-1 pitch to start the eighth.
If Colon is able to hold the Astros hitless the rest of the way, he'll become the first Ranger to throw a no-hitter since Kenny Rogers tossed a flawless game against the California Angels on July 28, 1994.
A leadoff walk to Carlos Correa and a Josh Reddick double ended the bid by Colon, who would have become the oldest pitcher to throw a no-hitter.
The right-hander has thrown 76 pitches and will take a bid for a flawless game into the seventh inning at Minute Maid Park.
Opposing fans in Houston gave Colon a standing ovation, and he clapped his bare hand softly against the outside of his glove. Colon is at 83 pitches.