Castro was awarded $5 million on Tuesday by arbitrators Matt Goldberg, Gary Kendellen and James Oldham, who heard arguments a day earlier. Castro had asked for a raise from $4 million to $5.25 million.
The 28-year-old was an All-Star in 2013. He hit .211 last season, his lowest average since his rookie season in 2010, and had 11 homers and 31 RBI. He made 102 starts at catcher and threw out 36 percent (24 of 66) of runners attempting to steal.
Castro started all six of Houston's postseason games and hit .063 (1-for-16).