Atlanta now owns the top-five most-attended matches in MLS history since moving into Mercedes-Benz Stadium late last summer.
Josef Martinez scored his league-leading 19th goal of the season for the Five Stripes three minutes after halftime to even the score. Nicolas Lodeiro's penalty kick in the 45th minute had put the Sounders ahead.
The point put Atlanta back in the lead in the MLS Supporters' Shield race, one point ahead of NYCFC.
“I’m calm with the production of the team today,” Atlanta United coach Tata Martino said. “It’s difficult to play against a defense that sits so far back and just plays very defensively. It’s difficult to break that defense down. I thought we did it pretty well at times, especially in the second half. But it’s hard to do."