Having seen defending champions PSG beat Toulouse 3-1 on Saturday and Lyon win 1-0 against Nantes earlier on Sunday, the pressure was on Marcelo Bielsa's men to perform at the Stade Geoffroy Guichard.
And the visitors looked to be on the way to maximum points midway through the second half, Michy Batshuayi scoring twice in the space of three minutes to give Marseille a 2-1 lead following Max Gradel's 54th-minute penalty for Saint-Etienne.
Gradel converted from the spot after Romain Hamouma was fouled by Jeremy Morel, who was partly at fault again in the first minute of injury time as former PSG striker Mevlut Erding snatched a point for the hosts.
Marseille failed to deal with a Yohan Mollo cross and Erding was able to out jump Morel to nod the ball in from point-blank range and hand Marseille a third straight draw that leaves them two points behind PSG and four adrift of leaders Lyon.
Lyon, meanwhile, were far from convincing versus Nantes, with forward Nabil Fekir turning home a fortunate winner in the 67th minute.
Fekir looked to have overran the ball from Alexandre Lacazette's neat flick-on, but Nantes defender Olivier Veigneau deflected it against his leg and into the net in an attempt to clear the danger as Lyon leapfrogged PSG to return to the top.
Guingamp suffered something of a European hangover as they followed up their 2-1 Europa League win over Dynamo Kiev with a 2-0 home defeat to Montpellier.
Goals from Morgan Sanson and Kevin Berigaud secured the points for the visitors, who missed a late penalty as Djamel Bakar struck the crossbar from 12 yards.
Elsewhere, bottom club Metz did their hopes of survival little good with a 0-0 draw at Reims.
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