Munster full-back Jeremy Staunton put a dampner on Gary Ella's first competitive match at Donnybrook as Leinster were beaten 15-8.
The match was marred by an injury to Rob Henderson that appears to have put paid to his World Cup chances.
The Celtic League curtain raiser went the way of the defending champions thanks to five penalties from the boot of Staunton in a tight, hard fought contest in front of a capacity crowd.
The home side took the lead when winger Brendan Burke applied the finish to a flowing movement in the fifth minute but as the match wore on, Munster began to gain the upper-hand up front.
With the Munster pack gaining a stranglehold, Leinster conceded too many penalties and after missing with his first two attempts, Staunton put on a flawless display of placekicking to secure the first points on the season.
Elsewhere, Ulster went down 41-30 to the newly formed Neath-Swansea Ospreys at the Gnoll.