The French defender swivelled to fire home midway through the second half at the Philips Stadion after Luuk de Jong had rose to head down a corner from the right.
Georginio Wijnaldum put the leaders ahead with a neat finish 11 minutes in after playing a one-two with De Jong, who then missed a chance to double PSV's lead when his penalty was saved by Sergio Padt.
Eric Botteghin headed the visitors level two minutes before the break, but Isimat-Mirin pounced to ensure Phillip Cocu's men remain 11 points clear of Ajax at the top of the table.
Champions Ajax responded to their UEFA Europa League defeat to Dnipro by dishing out a 4-1 hammering to Heerenveen.
Ajax were two goals up inside 11 minutes courtesy of a left-foot strike from Arkadiusz Milik and Davy Klaassen's header.
Joel Veltman then scored at both ends before Milik volleyed home a fourth goal before the home side's misery was complete when Pele van Anholt was shown a straight red card for a professional foul on Anwar El Ghazi.
Third-placed Feyenoord remain eight points adrift of Ajax and they needed a stoppage-time strike from Anass Achahbar - his first in the Eredivisie - to win 2-1 at bottom-of-the-table Dordrecht after Jeffrey Fortes had cancelled out Elvis Manu's opener.
Heracles moved out of the relegation zone with a 3-1 win at ADO Den Haag in the other Eredivisie game to be played on Sunday.
