The former president, in a wheelchair and neckbrace, was smiling when he took to the field with his wife. He then threw the first pitch to the Astros' Jed Lowrie.
Bush has been sporting a neck brace since he fell at his home in July and broke a vertebra in his neck.
Barbara Bush said she thought the first pitch was "great."
"We're big Astros fans," she said, according to Bush spokesman Jim McGrath.
Dad was first baseman in college. Took him all this time to figure out he was a pitcher. Nice W ‘stros! pic.twitter.com/aZcdjJEMbb— Jeb Bush (@JebBush) October 12, 2015
Today is Game 3 of the American League Division Series.
The Associated Press contributed to this report.