It had looked like PSG would suffer their first home loss in 20 Champions League group stage games when Dries Mertens put Napoli 2-1 ahead with 13 minutes remaining.
But Argentina international Di Maria whipped a terrific finish past David Ospina in the 93rd minute to deny Carlo Ancelotti victory against his former club.
PSG came into the game having never beaten Italian opposition in Europe's premier club competition and Lorenzo Insigne's first-half effort gave Napoli the lead.
The French side levelled when Mario Rui diverted Thomas Meunier's cross into his own goal but PSG continued to look suspect at the back.
A sign this might not be PSG's night arrived in the first two minutes as Neymar sustained an injury having been kicked by Edinson Cavani when the two got in each other's way.
Neymar was fine to continue and his team had plenty of chances, with Cavani missing a pair of opportunities, though PSG were given a warning when Mertens struck the crossbar.
Insigne was the next Napoli attacker to get behind the PSG backline in the 29th minute, and he collected Jose Callejon's delicious pass and lifted a finish over Alphonse Areola and into the net.
Ospina denied Kylian Mbappe, Neymar and then Meunier either side of the break as PSG pushed for a leveller.
With Insigne having been replaced seemingly due to an injury, PSG got their reward when a lovely move ended with a sliding Mario Rui diverting Meunier's cross past a wrong-footed Ospina.
Napoli would regain the lead through the quick-thinking Mertens after Marquinhos failed to deal with Fabian Ruiz's initial effort.
But Di Maria was afforded just enough space on his left foot to claim a late equaliser when he bent an unstoppable shot into the far corner from just outside the box.
What does it mean? Despite domestic dominance, PSG still not firing in Europe
In France, nobody can touch reigning Ligue 1 champions PSG, who have won each of their first 10 games in the division, but they have collected only four points from three matches in the Champions League. They may need to win in Naples next time out if they are to claim a top-two place in Group C.
Lethal Insigne continues fine form
Napoli went ahead through a cool finish from Insigne, who has now scored five goals in seven Champions League games. His side might have been out of sight early in the second half had he stayed on the pitch.
Cavani flops against former club
This was the first time Cavani had faced Napoli since leaving in 2013 and he entered the game with a glowing reference from president Aurelio De Laurentiis. His popularity among the Napoli faithful may have only increased after he spurned a pair of good first-half opportunities, while he was fortunate the offside flag spared his blushes when he somehow missed the target early in the second period.
Key Opta facts:
331 - Mário Rui's own-goal ended Napoli's run of 331 minutes without conceding in European competitions. Unlucky. #PSGNAP— OptaPaolo (@OptaPaolo) October 24, 2018
- Napoli are winless in six Champions League away games (D2 L4), extending their worst ever run in the competition.
- Napoli boss Carlo Ancelotti is winless in six Champions League games as manager in away ties against French sides (D3 L3).
- Lorenzo Insigne has scored eight goals in 11 games for Napoli in all competitions this season, more than double that of any teammate.
- Angel Di Maria has scored six goals in his last six starts at home for Paris Saint-Germain in the Champions League.
- Dries Mertens has been directly involved in 15 goals for Napoli in the Champions League since his debut in September 2013 (8 goals, 7 assists), at least six more than any other player.