Church's batting average led all National League rookies for the month, while he finished second with a .508 slugging percentage and a .406 on-base percentage.
"I'm rewarded for the hard work I put in," Church said. "It was a good month. Hopefully, it carries on. I know I can hit. I got off to a slow start, but I stayed confident and I have a game plan. If I go out and play like I know how, everything will work out."
Church hit just .190 in April, but he feels the turning point came on May 7 against the Giants, when he collected a career-high four hits and four RBIs in an 11-8 win.
The big hit came in the ninth inning of that game. With the score tied at 8, Church hit a bases-clearing double off right-hander Jim Brower to give the Nationals the lead.
"That hit really got me going," Church said. "I then went to Arizona, and I still hit the ball good."
Church will receive a specially designed trophy for winning the honor.
Other rookies receiving votes included Nationals teammate Gary Majewski; Brad Halsey and Lance Cormier of the Diamondbacks; Lance Niekro and Jason Ellison of the Giants; Jeff Francis and Clint Barmes of the Rockies; Kyle Davies and Ryan Langerhans of the Braves; and Yhency Brazoban of the Dodgers.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.