The Nationals and Astros entered game five of the best-of-seven baseball series tied at two games apiece after a pair of road wins for both teams. The matchup is the first World Series played in the U.S. capital since 1933.
Trump was seen waving and applauding from the grand stand during the game.
The hometown crowd cheered fans and soldiers displayed earlier on the screen, but there were some boos and isolated "Lock him up" chants when Trump appeared, according to a Reuters reporter in attendance.
He did not throw out the ceremonial first pitch and joked last week that he would look too heavy in the protective armor he would have to wear before taking the field at 41,000-seat Nationals Park.
Trump won just 4 percent of the vote in the
Class="kln">District of Columbia in the 2016 presidential election.
The U.S. capital is hosting its first World Series since 1933.