The Astros selected Bolton's contract from Triple-A Sugar Land on Monday, Chandler Rome of The Athletic reports.
To make room on the 40-man roster for Bolton, the Astros shifted Hayden Wesneski (elbow) to the 60-day injured list. Bolton has 34 games of major-league experience, all out of the bullpen, and has a career 5.79 ERA, 1.81 WHIP and 40:24 K:BB across 42 innings.