Castletroy opened the scoring with a penalty from out half Sean Moran but Munchin's hit back with tries from wing forward Matthew McSweeney and full back James Clancy for a 10-3 half time lead.
Munchin's were totally on top in the second half with their pack in complete control. Winger Edward O'Keeffe and center Dan Goggin added further tries and Ben Nugent kicked a conversion.
Scorers Castletroy College: Sean Moran pen.
St. Munchin's: Matthew McSweeney, James Clancy, Edward O'Keeffe and Dan Goggin tries, Ben Nugent 1 conversion.
Castletroy College: Jonathon McDonnell; David Grant, Eoghan Clancy, William Shanahan, Killian Carroll; Sean Moran, Luke Clohessy; Jack Tiernan, Liam Cronin, Stephen Shinners; David Butler, Pat Birmingham; Jack O'Neill, Ben Burns, Conor Bonfil.
Replacements: Robbie Sweeney, Mark Kennedy, Tom Kelly, Noel Clohessy, Daragh Kennedy, Brandon Foley-Friel, Mark McCarthy, Jack Murphy, Paul Butler, Sean Carey.
St. Munchin's College: Jamie Clancy; Edward O'Keeffe, Dan Goggin, Tom O'Neill, Diarmuid Morrissey; Shane Airey, Ben Nugent; Eoghan Kelly, Luke O'Halloran, Evan Ryan; Gavin Ryan, Ezra Nugent; Matthew McSweeney, Darren Ryan, Lee Nicholas.
Replacements: Daniel Montgomery, Daithi O'Byrne, David Begley, Ger Powell, Shane O'Mullan, Ryan Tsang, Cormac O'Donnell, Gary Bateman.
Referee: Olly Hodges (M.A.R.)