Thomas Tuchel's men had conceded late to draw against Bordeaux at the weekend, but it was the champion who had to come from behind to earn a share of the spoils at the Stade de la Meinau.
PSG was blunt in the first half and trailed to Kenny Lala's spot-kick after Thilo Kehrer was adjudged to have handled, but the Strasbourg hero turned villain with a wild swipe at inspirational substitute Kylian Mbappe that saw Edinson Cavani level with a penalty of his own.
There was late drama when Adrien Thomasson thought he had won it with a header for the host in stoppage time, only to be flagged offside.
Back-to-back draws represent the first minor wobble of Tuchel's Ligue 1 career and, given how PSG missed the injured Neymar and rested Mbappe before the break, the coach will hope to have both fit and firing swiftly.
PSG, 14 points clear at the top of the table, made a slow start, threatening only occasionally from crosses into a physical forward pairing, before the champion fell behind in controversial fashion five minutes before half-time.
Referee Antony Gautier was instructed by the VAR to consult the replay after Kehrer blocked a cross, with the official deciding after a lengthy delay that the ball struck the defender's arm - and not his chest - in the area. Lala stroked home the consequent penalty.
Mbappe was introduced at the break and his wonderful cross picked out Kehrer unmarked in front of goal, only for Matz Sels to make a superb instinctive stop.
Cavani was denied by an offside flag and then curled a free-kick just over, but he was on the scoresheet when Lala foolishly clattered into Mbappe.
However, PSG could not force a winner, with Sels saving again from Kehrer and then from Eric Choupo-Moting, and Strasbourg would have stolen the points but for a late Alphonse Areola stop to keep out Thomasson.
Thomasson came closer still in stoppage time, with an offside flag ruling out his close-range header.