The gymnasium is located on the second floor of the building, which used to be the original church, and is the sports hub for Saint Jerome School and CYO, Catholic Youth Organization, athletic programs. The school has a proud history of atiilctic success, whicl the gymnasium shows off with championship banners hanging in the rafters.

The gymnasium holds sporting events year round for boy's and girl's basketball and volleyball. The Saint Jerome School program boasts teams at the 'A', 8th & 7th grade, 'B', 6th & 5th, and 'C', 4th & 3rd, grade levels. The CYO sports program also gets ample use oi of the gymnasium. More than 15 schools in die Los Angeles area flood die gymnasium during the school and summer months. These are schools that either do not have their own gym or are not permitted to use the gym on dieir campus due to otiier functions.

In 1989 the hard gymnasium floor, which was and still is the original floor of die church, was refinished, giving it a nice glossy shine. Over the last 18 years however, the floor has deteriorated to the point where a new gym floor needs to be overlaid. Below is list of projects for the renovation of the gymnasium.