Marcellin College has a very strong, active and vibrant Old Collegians community. Former students continue a strong association with Marcellin beyond their school years in a variety of ways. The Marcellin College Old Collegians Association (MOCA) is an umbrella body which supports and promotes the many activities of the Alumni of the College. These groups include sporting clubs, such as the Old Collegians Football, Cricket and Soccer.

Many of our Old Collegians support our College through involvement in our senior retreat programs as well as outdoor education camps, social justice initiatives and other activities which draws on their experience of school and of the wider world. MOCA also assists in the organization of reunions of past students.