Castillo, 25, was batting .185 with two doubles, one home run and four RBIs in seven games. He injured his knee last Friday at Wrigley Field on the last pitch Kerry Wood threw in the eighth inning.
Castillo is the third catcher to go on the disabled list. Steve Clevenger, sidelined since April 26 with a strained right oblique, is currently rehabbing at Triple-A Iowa. He was the designated hitter on Tuesday and went 1-for-2 with a single. He could be ready when the Cubs return home Monday.
Geovany Soto, the Cubs' No. 1 catcher, was placed on the DL on Saturday after needing arthroscopic surgery on his left knee. He will miss three to four weeks.
Wood, 25, made his second start for the Cubs on Tuesday, taking Chris Volstad's spot in the rotation. In seven starts with Iowa, Wood was 3-3 with a 4.57 ERA.