Guus Hiddink's men reminded the rest of the teams in Holland that they face a real battle on their hands to grapple away their Eredivisie crown with goals from Andre Ooijer, Arjen Robben, Mark van Bommel, Mateja Kezman (two) and Park Ji-sung.
Willem were actually level in the game after Tarik Sektioui equalised Ooijer's opening goal after 10 minutes but the floodgates opened just after the half-hour mark when Robben restored PSV's lead.
Captain van Bommel added a third on 37 minutes before Serbia & Montenegro striker Kezman (pictured) bagged the first of his brace on the stroke of half time.
His second was to follow on 58 minutes before Korean Park Ji-sung rounded off the night with 27 minutes still remaining.
However, it is Ajax who find themselves top of the table with a 100 percent record after defeating RBC Roosendaal 1-0 at De Luiten.
Tom Soetaers scored the only goal on his debut to win the game for the Amsterdam club on 33 minutes.
Heerenveen will not be far behind them as they also maintained their winning start to the season with a 1-0 over Feyenoord who suffer their first defeat of the campaign.
Former Sheffield Wednesday striker Gerald Sibon scored the winner after just 17 minutes to send the crowd at Abe Lenstra Stadion into joyous celebration.
NAC Breda were 2-0 victors over Vitesse Arnhem at FujiFilm-Stadion.
Midfielder Ronnie Stam and defender Tamas Peto were on target for Breda to record their first points.
FC Utrecht had to settle for a point against ADO Den Haag.
Donny de Groot opened the scoring for Utrecht before Marcel Pronk netted an equaliser with just five minutes to spare.
Click below for full Eredivisie match stats
ADO Den Haag 1-1 FC Utrecht
Heerenveen 1-0 Feyenoord
NAC 2-0 Vitesse
PSV 6-1 Willem II
RBC 0-1 Ajax
click here for updated Eredivisie table
