Mustapha Yatabare's late goal looked to have given the home side a shock win against the league leaders.
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However, with two minutes remaining Alex evened things up for PSG when he nodded home a corner at the back post.
Edinson Cavani had a goal ruled out for PSG after the Uruguayan had strayed marginally offside.
Thibault Giresse had a chance for the hosts with 20 minutes remaining, but the midfielder couldn't keep his shot down on the edge of the box.
With the game edging to a goalless draw, Yatabare rose highest from a corner in the 84th minute to give Guingamp what appeared to be an unlikely victory against Laurent Blanc's side.
However, the former Chelsea defender scored even later to give PSG a share of the spoils.