UCD goalkeeper Billy Brennan scored and saved a penalty in the shoot-out as the students became the permanent holders of the Dr Tony O'Neill trophy.
The last ever final at this grade of the game pitted a UCD team seeking their third title in four years against a Pat's team chasing their first ever triumph at this level.
In normal time Timmy Purcell went closest to breaking the deadlock when he thundered a sixtieth minute strike off the Saints upright.
Extra-time was tense before Paul Byrne, Evan McMillan, Brennan and Forsyth netted for the Students.
Brennan's brilliant save from Daniel Corcoran helped UCD to maintain their stranglehold at this level.