 With the Phillies in 2010, Happ made three starts totaling 15 innings and earned a 1–0 record, 1.76 ERA, nine strikeouts, and a 1.63 WHIP.On July 29, 2010, Happ was traded to the Houston Astros along with minor leaguers Anthony Gose and Jonathan Villar in exchange for Roy Oswalt.He would make 13 starts with Houston in 2010, going 5–4 with a 3.75 ERA, 61 strikeouts, and a 1.32 WHIP in 72 innings.