The home team were still left frustrated however as Suwon played most of the match with ten match following the dismissal of Suwon left-back Yang Sang-min in the first half.
By that time, the Bluewings were a goal ahead thanks to a smart Lee Sang-ho shot after 23 minutes.
Seoul struggled to create chances after the break despite overwhelming possession. The leaders finally equalised with four minutes remaining thanks to substitute Jong Jo-gook.
With second-placed Jeonbuk Motors winning 3-0 at home to Busan I’Park, Seoul’s lead at the top was reduced to five points with six games of the season remaining.