The Westwood Regional High School Cardinals compete in the Big North Conference, which is comprised of public and private high schools in Bergen and Passaic counties, and was established following a reorganization of sports leagues in Northern New Jersey by the New Jersey State Interscholastic Athletic Association (NJSIAA). Before the NJSIAA's 2009 realignment, the school had previously participated in the Bergen County Scholastic League (BCSL) American Conference, which included public and private high schools located in Bergen County and Hudson County. With 628 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Group II for most athletic competition purposes, which included schools with an enrollment of 486 to 758 students in that grade range. The school was classified by the NJSIAA as Group II North for football for 2018–2020. Westwood Regional High School athletic teams are called the Cardinals. They wear school colors scarlet, white and black. The school's original colors were scarlet and white, with black added later as an official school color.