The away side took the lead on 17 minutes through Gael Danic, despite early pressure from PSG.
Ezequiel Lavezzi came close to finding an equaliser on 21 minutes, but his effort went wide of the post.
Thiago Silva broke free on 28 minutes and had a strike on goal, but he missed the target by some distance.
PSG continued to press Valenciennes, but they struggled to find a way to break down their backline.
Silva came close again on 38 minutes, getting up well in the area but just heading wide.
Much to the dismay of the Parc des Princes, Silva was shown a red card by the referee on 43 minutes, leaving PSG with 10 men for the second half.
© AP Photos
Zlatan Ibrahimovic has the first effort of the second half on 48 minutes, but the away defence closed down well.
Younousse Sankhare saw his strike on goal blocked by the PSG defence on 60 minutes as he looked to extend his side's lead.
Alex almost equalised for PSG on 70 minutes, but he couldn't direct his header on target.
The Brazilian central defender then lost his marker on 83 minutes and headed home to make it 1-1.