Neymar scored on his return from injury as Paris Saint-Germain beat Marseille 2-1 to win the French Super Cup in Lens on Wednesday to hand boss Mauricio Pochettino the first trophy of his managerial career.
Icardi, who has been struggling for goals this season, found the back of the net in the first half to set Ligue 1 champions PSG on the way to a routine win against last season's runners-up Marseille.
Icardi, who earlier had a goal ruled out for offside, put PSG ahead six minutes before the break from close range after his header was parried back into his path by Steve Mandanda.
Neymar replaced Angel Di Maria in the 65th minute for his first appearance in 2021.
He put on a convincing display, which was rewarded with a goal from the spot five minutes from fulltime after Icardi was brought down in the area by Yohann Pele.
Dimitri Payet pulled one back for Marseille in the 89th minute when he latched onto Florian Thauvin's cross, but PSG held firm to give new coach Pochettino his second win in three games with the capital side.
Pochettino, who last managed Tottenham Hotspur, had previously been beaten in the English Carabao Cup final in 2015 and the Champions League final four years later.