Referee Nicolas Rainville produced three red cards in quick succession early in the second half at the Stade de France, as the champions had Edinson Cavani sent off just moments after he had scored a penalty while Lens saw Jean-Philippe Gbamin and Jerome Lemoigne given their marching orders.
PSG coach Laurent Blanc was without a host of star names including David Luiz, Zlatan Ibrahimovic and Thiago Silva for the Ligue 1 clash, and Adamo Coulibaly opened the scoring after just 10 minutes following a swift Lens breakaway.
That put Lens boss Antoine Kombouare on top against his former club, but Yohan Cabaye levelled just before the half-hour mark, before Maxwell's delightful lob - which came after a poor piece of goalkeeping from Rudy Riou - put PSG in front.
Referee Rainville's decisions then proved the only second-half talking points.
Having awarded a soft spot-kick against Gbamin for a foul on Cavani, Rainville sent the defender off before showing two yellow cards to PSG's Uruguayan striker for his gun-firing celebration towards the crowd and then his reaction to his initial booking.
Lemoigne's dismissal, following a shove on Cabaye, restored PSG's numerical advantage, which they used to see out their first league win in three matches amid strange scenes at the national stadium.
Despite being depleted by injuries, PSG began brightly and Cavani fired into the side-netting after four minutes.
However, a quick Lens counter saw Coulibaly surging into the champions' box, with his calm sidefooted finish taking a nick off PSG captain Thiago Motta and deceiving keeper Salvatore Sirigu.
Blaise Matuidi then added to Blanc's fitness worries as he limped off with an apparent thigh problem, before Cabaye arrived late at the edge of the box and guided home his first league goal for PSG.
And Maxwell put PSG in front soon after with a perfectly executed lob from 35 yards.
Riou could only palm a long ball from Marco Verratti to the Brazilian, who took full advantage of the open goal as his precise right-footed lob left the backpedalling Lens goalkeeper wrapped up in the back of his own net.
Sirigu did well to keep out Coulibaly's header and ensure PSG went in ahead at the break, and Blanc's men extended their advantage soon after the interval when Cavani converted from the spot.
Cavani went down under minimal contact from Gbamin, who was shown a second yellow card for his indiscretion, before the striker himself was on the wrong end of some controversial refereeing from Rainville as PSG were reduced to 10 men.
Rainville was not finished there, either, as he capped off an incredible six-minute period by showing Lemoigne a second yellow for tangling with Cabaye inside the area.
PSG were able to see out the game with relative ease to maintain their unbeaten start to the season, but Cavani's suspension and a possible spell on the sidelines for Matuidi provides Blanc with yet more selection headaches.
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