The visitors came close to taking the lead when a cross came into the box from the right and Jeffrey Bruma rose highest in the area, but his headed effort clattered off the post.
PSV went ahead in the 12th minute when Gaston Pereiro lined up a strike from the edge of the area which sailed past Kostas Lamprou into the net.
Andres Guardado came close to doubling his side's advantage when he curled an effort over the wall from a free kick, but Lamprou made a good stop to deny the midfielder.
In the second half, Willem drew level when Erik Falkenburg rose highest in the box to head home a corner from the left beyond the reach of Jeroen Zoet.
The Netherlands stopped denied Falkenburg a second goal with a good save, but was powerless minutes later when the midfielder found the net to put the home side in front.
However, PSV hit back through De Jong as he turned the ball into the net with a low strike into the bottom corner, which proved to be enough to earn a point for Phillip Cocu's men.
Einhoven remain second in Eredivisie as a result of their draw, while Willem move into 16th place.