The 18-year-old Rabiot broke the deadlock one minute into stoppage time by tapping home after goalkeeper Mamadou Samassa had parried an Alex header into his path.
Ibrahimovic, last season's top scorer, sealed the victory two minutes later with his first goal of the season.
PSG's second consecutive win lifted them up to second with eight points from four games, one behind leaders Olympique Marseille, who host third-placed big spenders Monaco on Sunday.
Nevertheless, PSG showed they have room for improvement, and the Parc des Princes crowd booed the players off at the break.
While they had numerous chances and lacked some luck with the woodwork denying them twice, they could have gone one goal down if Guingamp striker Mustapha Yatabare had not spurned a one-on-one with keeper Salvatore Sirigu.
In the day's early kick-off, Kevin Berigaud scored twice in the first half as Olympique Lyonnais slumped to a 2-1 defeat at Evian TG, their fourth consecutive loss in all competitions.
The seven-time French champions, who were eliminated 4-0 on aggregate by Real Sociedad in the Champions League playoffs, had not lost four competitive games in a row since March 2009.
(Reporting by Gregory Blachier; Editing by Stephen Wood)
