Rain delayed the game by 1 hour, 11 minutes in the middle of the sixth inning.
Atlanta, which nearly blew a 7-0 lead, moved within 3½ games of NL East-leading Washington. The Nationals, who had won two straight and four of six, have lost 21 of 30 against the Braves.
Strasburg (8-10) gave up two more homers than his previous career high. He allowed seven runs, seven hits and two walks with nine strikeouts in five innings, dropping to 1-3 with a 6.99 ERA in seven starts at Turner Field.
Ervin Santana (11-6) held the Nationals scoreless until the sixth, when Asdrubal Cabrera had an RBI single and Anthony Rendon hit his 15th homer to make it 7-4.
Santana, who allowed four runs, four hits and two walks, struck out four in six innings and won his fourth straight decision.
Wilson Ramos’ fifth homer and Cabrera's sacrifice fly cut Atlanta's lead to 7-6 off reliever Anthony Varvaro in the seventh.
Craig Kimbrel earned his 33rd save in 37 chances by striking out Ramos, retiring Kevin Frandsen on a comebacker, and fanning pinch-hitter Danny Espinosa.
The Braves went up 2-0 in the first on Justin Upton's 20th homer, and they made it 6-0 in the second on B.J. Upton's eighth shot and Freeman's 16th.
Tommy La Stella put Atlanta ahead 7-0 in the fifth with his first career home run.
Washington's Denard Span went 3-for-4 with a run scored and reached base safely for the 34th straight game.
Nationals: RF Jayson Werth was given the night off because of a sore right ankle and right shoulder, but manager Matt Williams said he should be in the lineup for the series’ next two games. Werth's replacement, Steven Souza, hit the wall so hard in an attempt to catch Freeman's homer that his glove fell on the warning track. He stayed down on his back for about one minute but remained in the game after a trainer checked on him in right field. Souza lined out in his only at-bat before Frandsen replaced him in the fourth.
Braves: SS Andrelton Simmons missed his second straight game with a left ankle sprain, and manager Fredi Gonzalez said the earliest he might return is Monday when the Los Angeles Dodgers visit Turner Field.
Nationals: Tanner Roark (11-7) is coming off a 7-3 loss to Baltimore, his worst outing since May 3 against Philadelphia. Maybe a return to Turner Field will help Roark, who made his major league debut there with two scoreless innings of relief on Aug. 7, 2013. In 27 career starts and nine relief appearances, the right-hander is 18-8 with a 2.54 ERA.
Braves: Aaron Harang (9-6) has made 10 career starts against Washington, going 2-4 with a 3.72 ERA. He beat the Nationals 10-2 on April 13. The right-hander is 0-0 with a 2.88 ERA in four starts since the All-Star break.
LEGENDS ON DISPLAY
Former Braves pitchers Greg Maddux and Tom Glavine and manager Bobby Cox, who were inducted into the National Baseball Hall of Fame two weeks ago, each threw out a ceremonial first pitch.
The Braves have placed a patch on the front of their jerseys honoring Pete Van Wieren, a beloved broadcaster who died last Saturday. Van Wieren spent 33 years on radio and television, retiring in 2008 not long after the death of Skip Caray, his longtime partner in the booth.
The Uptons became the first set of brothers to homer five times in the same game as teammates, passing Jason and Jeremy Giambi and Vladimir and Wilton Guerrero.