The champions led 2-0 in the closing stages courtesy of first-half goals from Zlatan Ibrahimovic and Ezequiel Lavezzi, but were unable to hold on after losing four players to injury and finished the game with nine men.
Yohan Cabaye, Marquinhos, Serge Aurier and Lucas Moura sustained injuries and the home side were left two players down in the closing stages after making all three substitutions.
Caen made the most of their numerical advantage and stunned Laurent Blanc's side as Emiliano Sala pulled a goal back with two minutes to play before a stoppage-time free-kick from Herve Bazile snatched a point.
The draw ensured PSG were unable to return to the top of the table for the first time since December and leaves coach Blanc facing the prospect of being depleted for Tuesday's UEFA Champions League round of 16 first leg at home to Chelsea.
Midfielder Matuidi, who also picked up a knock and was substituted in the second half, rued the Parisian giants' misfortune but is not dwelling on the setback with a clash against Chelsea on the horizon.
He said: "We have to concentrate on our recovery now. It was a very cruel scenario pour the team, especially for the injured players. Beyond the result, it's the injuries that really hurt.
"We were in control and then bad luck struck us down. We are playing in every competition, that means a lot of matches and we are paying for all that effort.
"We have to stick together now and produce a great performance on Tuesday."
