The Blaugrana struggled in both halves of the field with Messi on the bench, but the arrival of their talisman in the second half helped them find the goal they needed to progress
With Lionel Messi at less than full fitness and consigned to the bench for over an hour, the Catalans appeared blunted up front, and were run ragged at the back by the ferocity of PSG's counterattacking approach.
And it was one such sequence that saw the Ligue 1 side break the deadlock minutes into the second-half, as Javier Pastore cleverly finished from Zlatan Ibrahimovic's through pass to round off a magnificent break.
But Messi's arrival in the latter stages of the second half swung the tie on its head, and with 71 minutes on the clock, a driving run from the Argentine was critical in setting up Pedro for a superbly taken equalizer.
The Blaugrana would hold on in the remaining minutes to ensure their progression, joining Bayern Munich, Borussia Dortmund and eternal rival Real Madrid in the hat for the last-four draw.
Cesc Fabregas was the man chosen to replace Messi in the home side’s front three, while for the visitors Zlatan Ibrahimovic, Thiago Motta and Maxwell all started against their former club, with David Beckham benched.
Xavi could have gotten the ball rolling as early as the third minute when his 20-yard free kick was curled agonizingly wide of the top corner, with Salvatore Sirigu beaten.
The pace of the match seemed to be picking up where the first leg’s emphatic finish left off, and Gerard Pique had to be alert to harry Exequiel Lavezzi off the ball from a dangerous run through on goal.
Lavezzi was proving himself to be a menace on the break, but his finishing let him down more than once. The Argentine drilled over the bar after wriggling free at the top of the box, before firing straight at Victor Valdes with the goal at his mercy.
Pedro forced Sirigu into a safety-first parry at the near post, missing the rebound to boot, but by far the better chances belonged to PSG, which, at times, had Barca on the ropes.
With half an hour gone, Ibrahimovic did excellently to stand a cross up at the far post, where Lucas connected with a header, but Valdes was there to tip over, and the keeper also stood tall to thwart Alex from the resulting corner.
But the tempo of the game would settle as halftime approached, as Barca began to regain some semblance of solidarity at the back, though its efforts in the final third remained nullified.
However, with one scintillating counter attack five minutes into the second half, PSG carved the Catalans completely apart. Lucas and Ibrahimovic were both involved, with the latter slipping in Pastore for a delicate finish.
Pastore could have had another just before the hour mark when he strode into the area to meet Ibrahimovic’s low cross, but this time he scuffed his shot.
Messi had already been put through his paces since the opening goal, and with 28 minutes remaining, he made his appearance off the bench, replacing the disappointing Fabregas.
And the Argentine was barely on the pitch for 10 minutes before making his presence felt, accelerating straight through the midfield and finding David Villa, who teed up Pedro to rifle home an exquisite equalizer from 18 yards.
Iniesta came close to putting the finishing touches on the tie with a mazy run through the defense with minutes remaining, but he could not place his angled finish anywhere but the side netting.
But despite a few nervy moments for Barca in the closing stages from set-pieces, time was simply not on PSG's side, and the Catalans held on to triumph.