The Chilean scored a stunner early in the first half for Barce, as Wakaso Mubarak's red card left the home side with little hope of a comeback, before Pedro sealed matters.
Alexis Sanchez opened the scoring in sublime fashion after a quarter of an hour for the visiting side, which was largely in control for the majority of the game, before Wakaso Mubarak's red card with 10 minutes to go essentially ended any hopes of an Espanyol comeback.
In the 86th minute, substitutes Xavi and Pedro combined excellently for the latter to poke home the clinching goal - Barca's 52nd away from home this season - marking a new record in the Spanish top flight.
Another landmark looms, as the Blaugrana's triumph in the derbi Barceloni moves the club to within three points of Real Madrid's 100-point tally from last season - which will be met should the club beat Malaga in its league finale next Saturday.
Sanchez was joined in the forward line by Cesc Fabregas and David Villa. All three player's sub-par campaigns have seen them face uncertain Barca futures, particularly with the impending arrival of Neymar from Santos.
But Sanchez could hardly have done more to convince Tito Villanova of his worth to the team next season than his fantastic moment of individual brilliance to get the ball rolling after 14 minutes.
The Chilean seemed to be running into a dead end after combining with Villa, but with supreme agility, he evaded two quick-fire challenges from Diego Colotto and Raul Rodriguez, before bending an exquisite finish into the far side.
It was a fairly comfortable opening to the game for Barca, though as expected, Lionel Messi’s absence denied the club's attack a certain element of panache, as Espanyol was able to hold its ranks at the back.
The stadium was then united in a minute of applause after 22 minutes, to commemorate former player Dani Jarque, who passed away in 2009 with a heart attack at the age of 22.
Espanyol, however, could count itself lucky not to have conceded a second goal just after half an hour, when Alex Song clipped a beautiful pass over the top of the defense to former Arsenal teammate Fabregas, whose finish struck the post.
Andres Iniesta also came close to notching his team’s second goal with a powerful strike that whistled the wrong side of the post moments before the interval.
Though the home side played with more poise after the restart, it was Villanova’s men who nearly struck first in the second half. A brisk move on the edge of the 18-yard area found Villa in space 12 yards out, but the striker could not find the target.
The second half had a distinct ‘end of season’ feel, as Barca seemed in no hurry to extend the lead, while Espanyol could not find an extra gear in the attacking third.
However, the game was thrown right back into the fire in the 80th minute when Wakaso picked up a yellow card, protested furiously, and was promptly given a second booking to put an end to his night.
The home fans, already testy after a few perceive refereeing injustices, were brought to their feet in fury by the Ghanaian’s dismissal, but were silenced for good with four minutes remaining as Barca struck again.
Xavi played the ball high into the path of Pedro inside the area, and the forward took the pass in his stride to flick a wonderful finish into the back of the net and kill off the game for good.