With Jose Alvarez pitching for the Angels, the Astros came up in the bottom of the ninth in a scoreless game. Jed Lowrie walked with one out, and after Colby Rasmus flied out Marwin González singled to center, setting up a two on, two out situation for Castro.
On a 1–2 count, Castro lifted a home run to right field to end the game.
Scott Kazmir made his Astros debut, pitching 7 2/3 innings and giving up three hits and no runs. Luke Gregerson picked up the win for Houston.
It was Castro's second career walk-off home run. He now has eight home runs on the season and is hitting .216.
The Astros entered the series with the Angels down one game in the AL West, but a sweep by Houston puts them two games up on Los Angeles.
Houston hosts the Arizona Diamondbacks on Friday.
- Molly Geary