The Argentinean scored two of his sides for tries and kicked 15 points as the Dublin side moved second in the League only two points behind Munster.
Tries from Brian Blaney and Shane Horgan catapulted Leinster to a 21-9 half time lead and despite periods in the sin bin for both Reggie Corrigan and Contepomi they were able to out gun the leaders.
Leinster struck a psychological blow on 22 minutes when they scored from a lineout drive straight out of the visitors´ textbook. With Peter Stringer caught in possession, the home side took on the set-piece and from a Malcolm O´Kelly take, young hooker Blaney plunged over.
Blaney´s first try for his province was added to by a Contepomi penalty, but with Munster´s forwards grinding out the hard yards, two place kicks from O´Gara cut the deficit back to 11-9.
However, winger Horgan struck on 37 minutes when, with a lot of work to do, he brushed aside the tackles from Anthony Horgan and David Wallace to sprint over at the right corner and touch down near the posts. Contepomi converted and added his third penalty, in injury-time, but the Puma star turned villain seven minutes into the second half when he was yellow carded for preventing a quick ruck release.
Munster made it a five-point game on 65 minutes when lock O´Connell spun out of tackles from Guy Easterby and Blaney to score and O´Gara converted.
Contepomi furthered his influence on the game on 74 minutes when he chipped over Anthony Foley and beat the cover to gather the kick and slide in at the posts.
Munster hit back again when O´Gara swung a skip pass out for replacement Halstead to sprint over at the right corner, but O´Gara´s excellent conversion mattered little in the end when Contepomi raced onto a loose ball 35 metres out and beat the covering Horgan and Halstead to touch down at the corner flag and convert for a famous victory