UCD produced a polished display at Belfield to see off last year's beaten finalists.
Walter Walsh burst through for a well-taken goal two minutes in, but Jamie Wall (0-3) drew the Limerick college level.
UCD's John Power and Mary's Colm Galvin swapped scores before Cathal Keane, Walsh, Jack Guiney (three) and David Treacy all scored for the Dublin 4 side.
But a goal from Wall ensured only three points separated the teams at the break (1-8 to 1-5).
UCD took the initiative with three points in quick succession from Cillian Buckley and Guiney (two). A neat finish by Keane on the stroke of 60 minutes and scores by Conor O'Shea and Guiney sealed the victory.
Scorers – UCD: J Guiney 0-7 (4fs, 1 '65'), W Walsh, C Keane 1-2 each, D Treacy 0-2, C O'Shea, C Buckley, J Power 0-1 each. Mary Immaculate: J Wall 1-5 (1-3fs), C Galvin 0-2, L Considine 0-1.
UCD – B Leydon; B O'Carroll, W Phelan, J Gannon; B Coughlan, M O'Hanlon, W Egan; J Lyng, C Buckley; W Walsh, D Treacy, P Murphy; J Power, J Guiney, C Keane. Subs: C O'Shea for Lyng (60), J McDowell for Power (60).
MARY IMMACULATE – N Kelly; N Wynne, C Barry, A Ryan; L Corry, S Kennedy, Eanna Hogan; C Galvin, T McGrath; J Hannon, D Reidy, L Considine; J Wall, B McCarthy, D Ferncombe. Subs: PJ Keane for McCarthy (49), Eoin Hogan for Considine (54), T Dowling for Ferncombe (54).
REF – B Gavin (Offaly).