The Marist High School Royal Knights / Lady Knights compete in the Hudson County Interscholastic League, which is comprised of private and parochial high schools in Hudson County, and operates under the supervision of the New Jersey State Interscholastic Athletic Association (NJSIAA). With 271 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Non-Public B for most athletic competition purposes, which included schools with an enrollment of 37 to 366 students in that grade range (equivalent to Group I for public schools). The school was classified by the NJSIAA as Non-Public Group II for football for 2018–2020.