The 20-year-old second baseman made history Monday with a two-run shot into the right-field seats off Atlanta's Touki Toussaint in the second inning.
The youngest player in the majors, Garcia was born on May 16, 2000. He was called up by the Nationals on Friday after Starlin Castro went on the injured list with a broken right wrist.
Garcia finished 1-for-5 in the 7-6 loss to the Braves.
The Associated Press contributed to this report.