Two goals in as many second-half minutes from Christian Stuani and Sergio Garcia effectively secured a win that was made to look more nervy after a late Obafemi Martins strike.
Espanyol dominated the opening period but relied on Vicente Iborra's own goal to hold a 1-0 half-time lead they relinquished almost immediately after the break to Ruben's clever header.
The hosts have lost just once in nine games under new boss Javier Aguirre, and they showed why they are on the rise as Stuani and Sergio Garcia combined to score the quickfire double which proved decisive.
Martins made Espanyol sweat when he fired in after 87 minutes, but they held on to go five points clear of the bottom three.
Espanyol dominated the opening period but only after Hector Moreno's goal-line lunge prevented them from slipping behind early on.
Martins' touch to get beyond onrushing goalkeeper Francisco Casilla was slightly heavy but Moreno still had to make up significant ground to get back and hack his shot off the line.
The hosts then took over and would have been more than 1-0 up at the break but for the profligacy of their on-loan Inter Milan forward Samuele Longo.
The 21-year-old first had an air shot after some scruffy build-up play before, at full-stretch, he failed to push the ball into an unguarded net after Joan Capdevila's left-wing run opened up the defence.
Espanyol eventually did get the goal they deserved, albeit thanks to poor Levante defending.
Simao Sabrosa fizzed a free-kick into the six-yard box where a panicked David Navarro headed the ball into team-mate Iborra's back before seeing it rebound over the line.
Levante did little in the first period but were on level terms almost immediately after the re-start following Ruben's quick thinking.
Home defender Diego Colotto attempted to help a hopeful high punt on to his goalkeeper but Ruben read his intentions and, after nipping in behind, showed quick reflexes to arch his body and guide a header home.
Despite the goal, Espanyol continued to play and were rewarded as Stuani and Sergio Garcia combined to fire them 3-1 ahead.
Stuani, who was wearing a face mask, headed his side back ahead on 68 minutes after Sergio Garcia stood a cross up to the far post.
Moments later Stuani returned the favour as he cut a pass back to Sergio Garcia, who coolly passed the ball beyond Gustavo Munua's reach.
Espanyol had to hang on though, as Martins expertly finished after racing behind Espanyol's high defensive line, and the Nigerian forced a late save from Casilla.