PSV were eager to continue their European season on a high note after beating Serie A champions Napoli 6-2 two weeks ago, making the away game at Olympiakos an exciting one as they looked to extend their win streak to six games.
A bright start wasn't to be for the visitors, who saw former Monaco man Gelson Martins get close in the opening minutes.
In-form midfielder Ismael Saibari saw a goal get ruled out for PSV after 12 minutes - a decision that'd come back to haunt the Eindhoven outfit, who conceded the game's opener just five minutes later through Gelson Martins.
A weak PSV created hardly any chances in the first half and saw Olympiakos dominate, despite having the bulk of the ball possession.
The visitors slightly improved following the break and nearly found an equaliser three minutes into the second half, but Ivan Perisic's effort couldn't beat Konstantinos Tzolakis.
The biggest chances of the half were nonetheless still for the hosts, who saw Gelson Martins hit the crossbar and later narrowly miss from inside the box.
Freshly brought on, Paul Wanner tried his luck from distance and got close, but ultimately saw his shot roll wide, making PSV's wait for a first shot on target pass the 70-minute mark. Fellow substitute Couhaib Driouech ended the wait after 77 minutes with an unimpressive attempt that Tzolakis easily stopped.
Despite the weak first 92 minutes, however, PSV still found a way past Tzolakis, who got his hands on a shot from Ricardo Pepi, but did not do enough to keep the American striker from scoring a 93rd-minute equaliser at the Georgios Karaiskakis Stadium.
PSV extended their unbeaten streak to nine games across all competitions, but saw their five-game win streak come to an end on the Greek coast.
Olympiakos, meanwhile, won their second point of the UEFA Champions League campaign and bounced back well from their 6-1 defeat to Barcelona.