The team said Friday that Doug Brocail will return as pitching coach and the team is bringing back Dave Clark (Shannon). General manager said the exact jobs for Trembley and Clark will be announced later.
The Astros have lost 100 games the last two seasons and have a new manager in Bo Porter.
Mallee, 43, was the hitting coach for the Miami Marlins while Trembley, 60, spent the last two seasons with the Atlanta Braves. In 2000 with the Cubs, Trembley managed Porter in Porter's first season in the majors.
The Astros also named Quinton McCracken as their new director of player development and promoted Allen Rowin to be his assistant.