Despite the hosts controlling possession on Tuesday night, Ezequiel Lavezzi and Javier Pastore netted in the first half to put Carlo Ancelotti's side in complete control and seemingly heading for the quarter-finals.
Adil Rami grabbed a last-minute lifeline for Valencia, though, and Zlatan Ibrahimovic saw red in the dying seconds to leave PSG facing up to a return leg without the services of their talismanic frontman.
PSG's late implosion took the shine off an otherwise impressive performance by Ancelotti's troops. Certainly the watching David Beckham, who recently joined PSG on a five-month deal but was not in the squad on Tuesday due to a lack of match fitness, will have been encouraged by what he saw.
However, that Lucas Moura played such an influential role for the Parisians will not have been lost on the 37-year-old, with the Brazilian's pace and trickery down the right channel not something the set-piece maestro can realistically expect to replicate.
Lucas was a thorn in Valencia's side in the opening period and had the first chance on nine minutes when he latched onto the ball after Ibrahimovic's run was halted and crashed an effort against the post.
PSG did not have long to dwell on that miss, however, as they took the lead 60 seconds later. Lavezzi started and finished the move, exchanging passes with Pastore on the edge of the area and advancing beyond the lunging challenge of Ricardo Costa before crashing a powerful finish beyond Vicente Guaita, who should perhaps have done better.
PSG's second goal arrived two minutes before the break, but again the Valencia goalkeeper will feel he could have done more.
Lucas, having impressed with a couple of surging runs from his own half, gave a demonstration of what he can deliver in the final third as he beat two men on the byline before running into the area and pulling the ball back for Pastore, whose first-time finish went through the legs of Guaita.
Valencia coach Ernesto Valverde shuffled his back at the interval, with striker Nelson Valdez and attacking midfielder Sergio Canales entering the action for Ever Banega and Jonas.
Valdez almost made an immediate impression when his back header from a corner was tipped over by Salvatore Sirigu under pressure from Roberto Soldado.
On 72 minutes PSG were denied a third when Clement Chantome turned the ball home after a good move following a free-kick, the substitute rightly ruled to have been coming back from an offside position.
Tino Costa's powerful free-kick drew a good parry from Sirigu in the 87th minute, but the PSG goalkeeper was culpable for Valencia's late reply, which gives Ernesto Valverde's men huge hope ahead of the return.
Costa created the chance with a chipped free-kick over the top of the Valencia defence, although as the ball floated into the six-yard box the goalkeeper should have come to claim. Instead, Sirigu stayed rooted to his line, leaving Rami unchallenged as he cleverly steered the ball into the net.
And with almost the very last action of the night PSG's efforts were further diluted when Ibrahimovic allowed himself to become riled as he challenged with two Valencia players and went over the ball in a challenge with Andres Guardado, prompting the referee to brandish the red card.