Phillip Cocu's men won five straight league matches before the international break and looked on course to extend their run when Luuk de Jong broke the deadlock shortly before the hour.
However, the hosts earned a share of the spoils with seven minutes left when De Leeuw stooped low to head home inside the six-yard box at the back post.
It marked PSV's first Eredivisie draw in exactly one year and they now lead champions Ajax by just two points.
The club are also sweating on the fitness of winger Andres Guardado, who was replaced in the 72nd minute by Jorrit Hendrix due to a reported ankle injury.
At the other end of the table, second-from-bottom Heracles secured a second win in three league matches in a 3-1 victory over ADO Den Haag at the Polman Stadion.
Mathias Gehrt put the visitors ahead, but Heracles roared back withthree goals in the space of 13 minutes before the break with Oussama Tannane's double sandwiching Thomas Bruns' effort, as Heracles won for just the third time this campaign.
A brace from Luc Castaignos helped third-placed Twente secure a come-from-behind 2-1 triumph at PEC Zwolle, the 22-year-old racking up his 50th career Eredivisie goal in the process.
Rounding off Sunday's Eredivisie action, Cambuur recovered from Ruud Boymans' first-half opener from the penalty spot to win 3-1 at Utrecht.