On December 13, 2017, Smith signed a two-year contract with the Houston Astros worth $15 million. In his first season in Houston, Smith appeared in 56 games, recording a record of 5-1 in ​45 ⁄ innings with a 3.74 ERA. On December 13 while working out, Smith suffered a ruptured left Achilles tendon. He underwent surgery for it on December 20.