Johnnie Jackson returned to haunt his old club by scoring one goal and making another as Colchester survived a late Swindon rally.
Jackson spent three months on loan at Swindon when he was a Tottenham teenager five years ago.
Swindon contributed to their own downfall with two defensive mistakes, but Colchester were nearly always in control from the moment Jackson put them ahead.
His goal came in the 32nd minute as the result of a long punt down the field by goalkeeper Dean Gerken, which was headed into Jackson's path by Clive Platt.
Jackson had plenty of time to drill home a left-foot shot into the corner of the net from the edge of the area.
Jackson turned provider in the 45th minute with a pass deep into the Swindon penalty area.
It should have been cut out by right-back Jack Smith, but he failed to control the ball and Scott Vernon had the easy task of scoring from eight yards.
Colchester remained in control until the 67th minute when Swindon were awarded a penalty when Matt Heath was adjudged to have handled a shot from Anthony McNamee.
Simon Cox stepped up to send Gerken the wrong way with his spot-kick to hand Swindon a lifeline.
With five minutes remaining, Swindon came close to scoring another when a corner on the left taken by substitute Mark Marshall was headed against the underside of the bar by Billy Paynter from ten yards.
Any chances of Swindon snatching a draw were ruined in the last minute and again there was a defensive mistake at the heart of the goal.
Mark Yeates sent the ball forward but it looked as if it easily be cut out by on-rushing goalkeeper Petr Brezovan.
But Brezovan completely missed the ball, allowing substitute Akanni-Sunday Wasiu to roll the ball into the empty net.
