Batting first, Leinster posted 243 for 5 from their 45 overs, with Lee Cole (79), and Ruairi Willis (68) both scoring half centuries.
The innings was dominated by two significant partnerships - Cole and Niall McGovern (43) put on an opening stand of 93, while the second wicket stand of 115 between Cole and Willis took Leinster virtually out of reach.
Best with the ball for Munster was Jack Marks (2-50).
In reply Munster battled bravely, and helped by Rory O'Keefe (45), and Cian Scannell (37), managed to post a more than respectable 166 for 8.
Ruairi Willis (3-21) completed a fine all-round performance, while Chris Wallace (2-33) also bowled well.
In the other fixture at Clontarf, the North West overcame a late wobble to beat their Northern counterparts from the NCU by three wickets.
Chasing 147 for victory, they were given the perfect platform by Jamie Huey (29), and Callum McGregor (28) who added 85 for the first wicket.
Some excellent bowling from Daniel McFadden (2-7), and Peter Ferguson (2-17) saw four wickets fall for just 8 runs, and the NCU were scenting victory.
However skipper Andrew Pierce in conjunction with Rishi Chopra got the NW over the finishing line with three wickets to spare.
Earlier the NCU had been indebted to the Templepatrick pairing of Jay Hunter (53*) and Daniel Gibson (18), who rescued their side from a precarious 68 for 7 to a much more healthy 146 all out.
Dean Curry (3-38), Jamie Magee (3-24), and Jordan Austin (2-29) were best with the ball for the NW.
The action today sees Leinster and the NW clash at Merrion, while NCU and Munster meet at YMCA - both games start at 11am.
At Rathmines, Leinster beat Munster by 77 runs
Leinster 243-5 from 45 overs (Lee Cole 79, Ruairi Willis 68, Niall McGovern 43, Jack Marks 2-50) Munster 166-8 from 45 overs (Rory O'Keefe 45, Cian Scannell 37, Ruairi Willis 3-21, Chris Wallace 2-33)
At Clontarf, NW beat NCU by 3 wickets
NCU 146 all out (44.1 overs, Jay Hunter 53*, David Gibson 18, Mark Adair 15, Jamie Magee 3-24, Dean Curry 3-38, Jordan Austin 2-29, Rishi Chopra 1-13)
NW 149/7 (43.1 overs, Jamie Huey 29, Callum McGregor 28, Jordan Austin 15, Daniel McFadden 2-7, Peter Ferguson 2-17).
