Cup specialists Clontarf held their nerve to edge past Terenure in a tense affair at Castle Avenue.
They had just one over and two wickets to spare as they chased down what looked like an under par Terenure total of 188.
Bill Coghlan's 51 and Eoghan Delany (45) put them in a strong position before a late flurry meant they were mightily relieved to creep over the finishing line.
Stephen Moreton top scored with 77, and Ru Jones chipped in with 40 in their innings.
Teenager Adam Craig and overseas professional Zander van der Merwe both picked up three wickets, while Bill Coghlan completed a fine all-round display taking 2 for 33.