The Cranford High School Cougars 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 participated in the Mountain Valley Conference. With 942 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Group III for most athletic competition purposes, which included schools with an enrollment of 761 to 1,058 students in that grade range. The school was classified by the NJSIAA as Group IV North for football for 2018–2020.