Castro hit .579 (11-for-19) last week, with one double, three home runs, five RBIs and five runs scored in six games to claim his first career weekly honor. He's the first Astros player to earn the honor since Hunter Pence won it for the week ending Sept. 5, 2010.
Castro led the Majors in average, slugging percentage (1.105) and on-base percentage (.636) over the seven-day stretch. He was also tied for fourth in homers and tied for fifth in total bases (21).
"It's a great honor," he said. "I'm humbled and really appreciative of receiving the award. It's exciting. I'm very grateful for the opportunities I've been given here."
In Houston's 3-1 win over the Royals on Wednesday, Castro went 3-for-4 with a double, an RBI and a run scored while also throwing out two runners on the basepaths. He hit two more home runs on Saturday in the Astros' 11-5 loss to the A's.
Castro and teammate Matt Dominguez each hit a pair of homers in that game, becoming the first pair of Astros to hit multiple long balls in the same game since Lance Berkman and Craig Biggio on July 25, 2005.
Castro has six homers this season, equaling his 2012 total and matching his career high. With a four-hit effort on Sunday against the A's, Castro became the first Astros player with at least three hits in three straight games since Ty Wigginton did so from Aug. 15-17, 2008.
Joey Nowak is a reporter for MLB.com. Follow him on Twitter at @joeynowak. Astros beat writer Brian McTaggart contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.