Castro, 22, singled in the third for hit No. 499, and then singled with two outs in the fifth for No. 500.
The only other active player on the list is the Yankees' Alex Rodriguez.
Others to reach the milestone at such a young age include Ted Williams, Hank Aaron, Al Kaline, Mickey Mantle, Robin Yount, Ty Cobb, Johnny Bench, Orlando Cepeda and Ken Griffey Jr.
Since Castro made his Major League debut on May 7, 2010, he leads all National League players in hits. The Brewers' Ryan Braun was next with 490 hits entering play on Friday.