In September 2004, the school moved to its new permanent facility at Mavis Road and Courtneypark Drive West.

The state of the art institution is part of a shared facility agreement with the City of Mississauga.

[2] This library is a shared facility between the City of Mississauga and the Dufferin-Peel Catholic District School Board.

[3] In March 2010, a routine chemistry experiment at St. Marcellinus exploded into flames when a Bunsen burner ignited a beaker full of methanol.

During this time, St. Marcellinus was placed under lockdown and Mississauga Secondary was placed in a hold and secure until the police confirmed that there was no longer a threat.