The Braves have won four straight, six of seven and 16 of 25 since the All-Star break, a stretch that has made them a factor in the NL playoff race. Atlanta started the sweltering night 4.5 games behind NL East-leading Philadelphia, which visits Turner Field this weekend.
Hanson (7-2) had his second-most strikeouts since being called up from Triple-A in early June, surpassed only by an 11-strikeout effort against San Francisco on July 20. He allowed seven hits and didn't walk anyone.
Chipper Jones, back in the Atlanta lineup after missing three straight games with a strained oblique muscle, hit a mammoth homer that reached the second section of seats in right field.
The Nationals' eight straight wins were the second-longest streak since the franchise moved to Washington four years ago, surpassed only by a 10-game run in June 2005.
Washington jumped ahead in the first inning, even though Hanson struck out the side. Nyjer Morgan led off with a single, stole second and scored on Ryan Zimmerman's one-out single, which extended his hitting streak to 14 games.
The Braves tied it in the second, taking advantage of consecutive walks by John Lannan (8-9) to start the inning. Garrett Anderson singled to load the bases with no outs, but Atlanta managed only one run. Matt Diaz grounded into a double play, scoring Brian McCann, and Omar Infante flied out to end the threat.
Morgan was in the middle of things again in the third. He singled with one out, stole second and tried to swipe another base, appearing to get his hand on the third-base bag ahead of Jones' tag. But umpire Larry Vanover called the speedy runner out.
The Nationals were especially enraged when Cristian Guzman followed with a single stretching his hitting streak to 16 games but failing to produce a run. Hitting coach Rick Eckstein began yelling from the dugout and was ejected. He charged onto the field to carry on the argument and had to be restrained by manager Jim Riggleman.
After that brouhaha, the Braves pulled ahead for good in the bottom half. Martin Prado doubled in a run and wound up scoring when left fielder Josh Willingham bobbled the ball after fielding Jones' single.
Atlanta broke it open with a three-run fifth that knocked out Lannan. Ryan Church picked up an RBI with a ground-rule double, then McCann and Yunel Escobar came through with two-out, run-scoring hits.
Lannan went 4 2-3 innings, giving up six hits and six runs (five earned). He walked four and struck out one.