Ola Kamara scored twice in the first half, but also picked up a pair of yellow cards and was sent off in stoppage time. Austin then got goals from Danny Hoesen, Sebastian Driussi and Ruben Gabrielsen over the final ten minutes.
Austin won on the road for the first time in nearly a year and their comeback was the fifth time in MLS history a team won after overturning a two-goal deficit in the 80th minute or later.
Story of the match
DC United thought they had the opening goal in the seventh minute as Julian Gressel's pass from deep in his own half broke Austin’s lines and sent Kamara in alone to fire past Brad Stuver, only for the offsides flag to go up.
Austin was nearly on the scoresheet 15 minutes into the match as Maxi Urruti picked the ball off of DC United goalkeeper Bill Hamid, but slipped as he shot, which went well over.
Jackson Hopkins, making his debut for the Black and Red, missed narrowly wide in the 25th minute and Kamara then gave the Black and Red the lead a minute later as Gressel crossed for Andy Najar and his centering header that the Norwegian finished past Brad Stuver.
On the half-hour mark, the visitors thought they had equalized through Diego Fagundez, but offsides in the build-up play negated the goal.
The hosts then doubled their advantage as Gressel and Chris Durkin played a neat give-and-go with the former getting the ball back to Kamara, whose one-timer found the back of the right side of the net.
Julio Cascante hit the crossbar with a header in the 45th minute and Kamara, who picked up a yellow card for taking off his shirt after his first goal, was given his marching orders after a foul on Driussi.
The comeback began in the 80th minute when Fagundez' corner fell into the goalmouth and Hoesen finished with a volley without so much as a challenge.
Five minutes later, Driussi converted Hector Jimenez' cross at the back post and after a lengthy check of VAR, the goal stood to make it 2-2.
Austin completed the turnaround in the 90th minute when Felipe Martins served a ball at the back post for Gabrielsen, his angled header deflecting off of Hamid's right hand.
Man of the match: Diego Fagundez
His two assists showed how he is not only one of the key players for his abundant talent, but how he kept his side emotionally grounded, allowing them to take all three points.