After a goal-less first half that saw Pune FC dominate the proceedings, United SC brought the turnaround through a superb Lalkamal Bhowmick goal in the 68th minute, while Ranty Martins completed the tally in the 85th minute.
Having pocketed a second straight win, with their last one coming against defending champions Dempo, the Eelco Schattorie-coached side climbed to the top five in the table with 20 points.
For the otherwise consistent Pune FC (28 points), it was their first loss in nine matches as they missed a fine chance to consolidate their position atop the standings.
Pune FC looked the better side at the start and were unfortunate to have missed a 2-0 lead at the interval.
The Derrick Pereira-coached side almost took a 12th- minute lead when striker James Moga from the right flank had a fine control of the ball, but his shot from inside the box found the side netting.
After nine minutes, a surging Moga got the ball from a counter attack as the striker cut back on the top of the box to set up an unmarked Douhou Pierre who only shot it over.
The miss proved to be costly as Bhowmick turned the match around with a beautiful measured long-ranger.
Deepak Mondal's cross from the right was headed out by a PFC defender but Bhowmick on the run volleyed it over custodian Abhra Mondal from a distance.
Ranty doubled the lead from a Deepak Mondal counter as Pune FC defence failed to clear.
The Nigerian showed fine control as he finished with a powerful rightfooter to the left of an outstretched Abhra Mondal to settle the issue.
