Phillip Cocu's side suffered a 1-0 UEFA Europa League defeat at home to Zenit on Thursday, but responded by securing an 11th consecutive league victory in bottom side Dordrecht's first game since coach Ernie Brandts' departure by mutual consent.
The runaway leaders were in front after only four minutes at the Philips Stadion, when Jetro Williams' cross was turned into his own net by Jeffrey Fortes.
Dordrecht were unfortunate not to be level when Matthew Steenvoorden's header rattled the crossbar, but any hopes of a comeback looked to be ended by a Luuk de Jong penalty 62 minutes in.
Jeffrey Bruma added a third goal 20 minutes from time as PSV took another giant stride towards winning their first Eredivisie title since 2008.
Ajax's hopes of retaining the title look even slimmer after they could only draw 1-1 at mid-table Willem II.
Anwar El Ghazi struck the post before Arkadiusz Milik, scorer of the only goal of the game in the Europa League win over Legia Warsaw on Thursday, put the champions in front eight minutes before half-time.
That was not enough to secure all three points, though, as Ali Messaoud levelled seven minutes into the second half and Ajax, who face a trip to PSV next weekend, were unable to fashion a winner.
Tom van Weert's first-half double had put the visitors on course for a shock victory, but the turning points came five minutes into the second half when Jurgan Mattheij was sent off for handball and the in-form Colin Kazim-Richards converted the resulting penalty.
Twente suffered have now lost their last four games after Vitesse consigned them to a 2-1 home defeat, while Heerenveen were 3-1 winners against Groningen.
