PSG appeared to be heading for defeat 11 minutes before half-time when Andre Ayew gave Marseille the lead from the penalty spot following Thiago Motta's foul on Mathieu Valbuena, with the Italy international also being shown a red card.
However, the defending Ligue 1 champions overturned the deficit despite Marseille's numerical advantage, with Maxwell equalising with a header on the stroke of half-time, before Zlatan Ibrahimovic netted the winner from the spot after Ayew had brought down Marquinhos.
The win was PSG's first at the Stade Velodrome for five years, and ensured that they stayed level on points with newly promoted Monaco at the top of the table.
And Blanc was quick to express his delight at the nature of the victory.
"The will was a very important element of this game because without it we could do nothing," he said.
"There was also an impressive solidarity and quality in the game.
"For this kind of game you need good players and a good state of mind.
"We always believed despite the penalty and the red card. At half-time we were glad to have equalised but we wanted to win."
PSG will look to continue their unbeaten start to the season after the international break when they welcome Bastia to the Parc des Princes.
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