Barcelona started the day eight points clear of Real Madrid, who host fourth-placed Real Betis on Wednesday, but their local rivals frustrated them with a robust defensive display.
Miguel Angel Lotina's side, who moved up to fourth in the standings, finished the game with 10 men after defender Daniel Jarque received a straight red card in the 66th minute.
Barcelona pressurised Espanyol throughout the second half and created a number of scoring opportunities, but Kameni and his defenders held firm to leave Barca nine points clear at the top.
La Liga's top scorer Samuel Eto'o had the perfect chance to put Barca ahead inside the opening minute as he cut into the visitors area and fired goalwards, but Kameni made his first intervention of the night to turn the shot wide with his foot.
Espanyol's five defenders weathered a nervy opening period but effectively smothered out most of the home side's attacking impetus and Kameni had little to do until after the interval.
With playmaker Ivan de la Pena suspended, and striker Raul Tamudo injured, Espanyol struggled to create much on the counter and failed to test Barca keeper Victor Valdes throughout the game.
Barca coach Frank Rijkaard made a tactical change at halftime, withdrawing striker Maxi Lopez and midfielder Gerard Lopex replacing them with Juliano Belletti and Andres Iniesta in an attempt to create more goalscoring opportunities.
The changes produced the desired result for Rijkaard and within minutes Kameni came to the rescue once again with a stunning one-handed save from a driven Iniesta shot.
Barca's wide players found more space and created a number of chances for Eto'o but Espanyol defender Antonio Soldevilla, and Kameni, stopped the Cameroon international adding to his tally of 17 league goals with desperate defending.
Jarque's dangerous challenge on Rafael Marquez earned him a straight red card with 24 minutes remaining, but Barca failed to take full advantage of the extra man.
