Jody Morris is still searching for a first point as Swindon manager after Sutton snatched a dramatic 2-1 victory at Gander Green Lane.
The hosts saw an early Enzio Boldewijn effort ruled out for offside.
Swindon went in front through Charlie Austin after a neat move on the left allowed Frazer Blake-Tracy to tee up the former QPR striker to score his fourth goal in five appearances since signing last month.
Austin came close to doubling his tally as he fired wide of the mark.
Sutton goalkeeper Jack Rose kept the hosts in the game as he saved Luke Jephcott’s free-kick before twice deny substitute Jacob Wakeling.
And when Sutton substitute Matt Dennis rattled the crossbar with eight minutes left, it looked like a point would elude the hosts.
But goalkeeper Sol Brynn failed to hold Joe Kizzi’s cross and Lee Angol, who had earlier come off the bench, levelled for Sutton with five minutes left.
And Ali Smith completed a fine turnaround two minutes from time when he forced home David Ajiboye’s cross.
