The Catholic Youth Organization, or CYO, is a parish-based youth program that gives Catholic youth the opportunity to play various sports, participate in programs, and contribute to service projects within their community.  Encompassing Chester, Bucks, Delaware, Montgomery, and Philadelphia Counties, the CYO contains 14 Regions and over 150 Catholic elementary schools.

St. Mary's CYO competes in Region 18-21 which includes Holy Family, Holy Rosary, Immaculate Heart of Mary, Mother of Divine Providence, St. Aloysius, St. Basil, St. Eleanor, St. Helena, St. Philip Neri, St. Teresa of Calcutta, and Visitation.