Harper drove in five runs. His third-inning grand slam just cleared the reach of leaping Braves center fielder Ender Inciarte. Harper's seven career homers off Teheran are his most against any pitcher.
Ryan Zimmerman added an eighth-inning grand slam off Ian Krol, sending some Braves fans for the exits at new SunTrust Park. The Nationals had 20 hits.
Washington's Joe Ross (1-0) allowed three runs on six hits in seven innings in his 2017 debut.
Teheran (1-1) allowed seven runs on seven hits in four innings.
Nationals outfielder Jayson Werth left the game during a third-inning at-bat with an undisclosed injury. He appeared to suffer the injury on a check swing.
