The Union Catholic High School Vikings compete in the Union County Interscholastic Athletic Conference, which is comprised of public and private high schools in Union County and was established following a reorganization of sports leagues in Northern New Jersey by the New Jersey State Interscholastic Athletic Association (NJSIAA). Prior to the NJSIAA's 2009 realignment, the school had participated in the Mountain Valley Conference, which included public and private high schools in Essex, Somerset and Union counties. With 614 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Non-Public A for most athletic competition purposes, which included schools with an enrollment of 381-1,454 students in that grade range (equivalent to Group I for public schools). Dave Luciano is the Athletic Director.