The match got off to a frantic start when Joan Verdu's back-post header was saved by visiting goalkeeper Victor Valdes. The midfielder was first to the rebound, but his shot cleared off the line by Gerard Pique.
Barca had a goal ruled out soon after when Cesc Fabregas tapped in following Lionel Messi's interception of keeper Cristian Alvarez's pass. However, the referee cancelled the goal out for a dubious handball by Messi.
Fabregas legitimately found the net minutes later when he powered a header past Alvarez from Dani Alves's cross.
Fabregas had a chance to double his side's lead just before the break, but his solo effort was tipped wide by the keeper.
Espanyol could have been reduced to ten men on the stroke of half time when Romaric appeared to elbow Pique when the pair challenged for an aerial ball.
Alves saw his shot easily saved by Alvarez just after the interval before the Brazilian had a goal ruled out for offside.
A tentative period of play followed before Xavi curled his free kick over the bar.
Messi nearly grabbed a second for Barca with 15 minutes to go, but his right-footed shot hit the post from a tight angle.
Espanyol grabbed their equaliser with five minutes to play when Alvaro Vazquez nodded in Thievy Bifoum's flick-on from Raul Rodriguez's cross.
Barca nearly found a winner in injury time when Pique's shot bounced back off the post to Pedro, whose shot was then blocked on the line.