The Brazilian converted a Kylian Mbappe assist in first-half stoppage time to decide a hard-fought encounter with chances at both ends and a red card for Marseille defender Samuel Gigot.
He was sent off in the 72nd minute for scything down Neymar, whose theatrical reaction may have helped convince the referee to produce a red card instead of a yellow.
It is a welcome return to winning ways for PSG after three straight draws – two of which came against Benfica in the Champions League – and a week overshadowed by new doubts about Mbappe's future at the club.
PSG are three points clear of surprise package Lorient, who drew 0-0 on Saturday with Reims.
Lens are five points behind the leaders in third, with Marseille another point adrift now in fourth after their second successive domestic defeat.
Mbappe lined up for the Parisians despite the reports this week that he wants to leave the Qatar-owned club at the earliest possible opportunity.
The France superstar has not yet spoken out publicly to confirm or deny the reports which surfaced in Spain ahead of Tuesday's game against Benfica and were later also reported by various French media.
Lionel Messi returned for Christophe Galtier's side after missing the last two games with a minor injury, and the Argentine was desperately unlucky not to find the net from a first-half free-kick.
After being fouled just outside the area, his dead-ball strike from a little over 20 metres hit the underside of the crossbar and bounced away off the line.
Before that Mbappe was twice denied by fine saves from Marseille goalkeeper Pau Lopez, while PSG lost Danilo Pereira to injury early on.
The Portugal midfielder has been standing in at centre-back with Presnel Kimpembe injured, while Sergio Ramos was suspended here.
PSG will hope Pereira's injury is nothing serious, as will the player with the World Cup now just over a month away.
Marseille were a threat too when they got forward but the home side went ahead two minutes into added time at the end of the half.
Marco Verratti won back possession high inside the Marseille half before Mbappe set up Neymar to slot a first-time shot low into the corner for his ninth league goal of the campaign.
Marseille, who beat Sporting Lisbon in the Champions League in midweek, could not find an equaliser in the second half and were handicapped by the loss of Gigot for his lunge on Neymar.