Marys make it three wins in a row
Goals from Craig Murphy, Karl Clarke and Jack McVey were enough to give St Mary's victory from their trip to defending champions St George's.
It keeps them at the top of the Canada Life Premier League on goal difference, with St George's now five points off the pace.
Jay Skelcher-Maxwell had given the hosts a first-half lead at Glencrutchery Road, and a late Ciaran McNulty strike ensured a nervy finish.
However, Mary's held on for the three points to make it three wins in succession.