Zlatan Ibrahimovic saw red as David Beckham watched goals by Ezequiel Lavezzi and Javier Pastore secure a win for Paris Saint-Germain in Spain.
PSG looked on course for a dream result as first-half goals by their Argentinian duo Lavezzi and Pastore put Carlo Ancelotti's men firmly in the driving seat but their hopes of reaching the quarter-finals suffered a setback in the space of two wild minutes at the end of the contest.
First Adil Rami stole in behind the defence to reduce the arrears for Los Che before PSG's talismanic striker Ibrahimovic was dismissed for aiming a stamp at Andres Guardado.
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Doubling up: Javier Pastore (right) scored Paris Saint-Germain's second of the evening
Excellent start: Ezequiel Lavezzi (right) is hoisted up by Zlatan Ibrahimovic after opening the scoring for PSG
Needless: Zlatan Ibrahimovic was red-carded by referee Paolo Tagliavento for a stamp
Valencia: Guaita, Rami, Joao Pereira, Guardado, Costa, Oliveira (Valdez 46), Feghouli (Viera 83), Banega (Canales 46), Parejo, Facundo, Costa, Soldado
Subs not used: Diego Alves, Ruiz, Albelda, Piatti
Booked: Joao Pereira
Goal: Rami 90
Paris Saint-Germain: Sirigu, Sakho, Alex, Maxwell, Jallet, Matuidi, Verratti, Pastore (Armand 88), Lucas Moura (Chantome 53), Lavezzi (Menez 76), Ibrahimovic
Subs not used: Douchez, Camara, Van Der Wiel, Gameiro
Sent off: Ibrahimovic 90
Goals: Lavezzi 10, Pastore 43
Referee: Paolo Tagliavento (Italy)
The red card means Ibrahimovic is suspended for the return leg along with defensive midfielder Marco Verratti, who picked up his third booking of the campaign.
PSG's late implosion took the shine off an otherwise impressive performance by Ancelotti's troops.
Certainly Beckham, who recently joined PSG on a five-month deal but was not in the squad 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 has in his locker.
Lucas was a thorn in Valencia's side in the opening period and had the first chance on nine minutes when he latched on to 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.
Marching orders: Ibrahimovic will miss the next leg of the tie
Consolation: Adil Rami gave Valencia hope of progressing after cutting PSG's advantage in half late on
Colossus: Ibrahimovic holds off the challenge of Tino Costa
Making a mark: Salvatore Sirigu (centre) catches the ball to halt a Valencia attack
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.
Guardado flashed an effort over the bar as Valencia went in search of the leveller, but it was PSG who looked most likely to add to the scoring, with Lucas and Lavezzi bringing saves from Guaita.
PSG's second goal arrived two minutes before the break, but again the Valencia goalkeeper will feel he should have done better.
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.
Aerial battle: Christophe Jallet (left) is unable to compete with Ever Banega in the air
Anguish: David Beckham and Leonardo (right) watch the tie
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.
Lucas' impressive outing was ended on 53 minutes as Ancelotti sacrificed the attacking flair of the Brazilian for the more defensive midfield option of Clement Chantome.
Chantome's added midfield bite was unable to prevent Soldado getting in behind the visiting defence on 61 minutes, the striker running on to Tino Costa's lofted pass only to see the chance come to nothing as his heavy touch took the ball away from goal.
On 72 minutes PSG were denied a third when 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.
Making an appearance: David Beckham (centre) was inside the stadium to support his new team-mates
Valdez passed up a glorious chance to get Valencia back into the contest when he stole in ahead of Alex to reach another lofted pass by Costa, but the striker shanked his left-footed finish into the side-netting.
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 Valverde's men huge hope ahead of the return.
No chance: Blaise Matuidi (right) snatches the ball away from Daniel Parejo (left) of Valencia
Flare up: Visiting Paris Saint-Germain fans set off a flare in the stands
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 Guardado, prompting the referee to brandish the red card.
Star man: Lavezzi (left) was in exceptional form and looked a constant threat
Tussle: Matuidi and Banega (right) battle away in the middle of the park
Video: watch Zlatan's sending off