The Northern Valley Regional High School at Demarest Norsemen compete in the
Big North Conference, a
super-conference comprised of public and private high schools in Bergen and
Passaic counties established in 2009 as part of an effort to achieve greater competitive balance between schools, following a reorganization of sports leagues in Northern New Jersey by the
New Jersey State Interscholastic Athletic Association. The school had previously competed in the
North Bergen Interscholastic Athletic League, an athletic conference that consisted of high schools located in Bergen County. With 762 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 football team competes in the Patriot Red division of the
North Jersey Super Football Conference, which includes 112 schools competing in 20 divisions, making it the nation's biggest football-only high school sports league. The school was classified by the NJSIAA as Group III North for football for 2024–2026, which included schools with 700 to 884 students. The school offers over 23 sports, which include participation at the freshman, junior varsity, and varsity level (46 teams), as well as 18 co-curricular activities. Sports include bowling, football and boys' and girls' basketball, and volleyball. The boys indoor track team was Group III champion in 1961 and won the Group II title in both 1964 and 1965. The boys' tennis team won the Group III state championship in 1973 (defeating
Princeton High School in the tournament final) and 1979 (vs.
Summit High School). The 1973 team finished the season with a 22–3 record, which included defeating Princeton 4–1 in the tournament final for the Group III title. In 1997, the boys' tennis team went undefeated at 15–0 to claim the NBIL league championship, under head coach Dan Moses. In 1977 and 2019, the boys soccer team won the Bergen County championship. The softball team won the Group III state title in 1979 (against runner-up
Bridgeton High School in the finals of the playoffs) and won the Group II championship in 2016 (vs.
Arthur L. Johnson High School). The 1979 team finished the season with a record of 25–2 after winning the Group II title defeating Bridgeton by a score of 3–2 in the championship game. The team won the 2016 Group II title with a 9–3 win in the tournament's final game against Arthur L. Johnson High School. The field hockey team won the North I Group III state sectional final in 1984, 1992, 1994 and 2007. In 1997, the team won the Northeast Field Hockey League Championship and also the Bergen County Championship beating
Northern Highlands Regional High School by a score of 1–0 in the tournament final. In 2007, the field hockey team won the North I, Group III state sectional championship with a 19–0 win over
West Morris Central High School in the tournament final. The girls' tennis team won the Group III state championship in 1989 (defeating
Montville Township High School in the tournament's final match) and 2019 (vs.
Holmdel High School). The 2019 team won the Group II title, defeating five-time defending champion by 4–1 at
Mercer County Park in the final match of the tournament. The football team won the North I Group III state sectional championship in 1992. The baseball team won the Group III state championship in 1999 vs.
Middletown High School South in the playoff final. The baseball team won three Bergen County Championships in years from 1991 to 1995. The girls' volleyball team won the Group III state championship in 2000 (defeating
Paramus Catholic High School in the last match of the tournament), 2001 (vs.
Ramapo High School), 2002 (vs.
Northern Valley Regional High School at Old Tappan), 2003 (vs. Old Tappan) and 2014 (vs. Old Tappan), and won the Group II title in 2006 (vs.
Chatham High School), 2012 (vs.
Sterling High School), 2018 (vs.
Rutherford High School) and 2019 (vs. Rutherford); the program's 10 group titles are tied for fifth-most of any school in the state. The team won the inaugural
Tournament of Champions in 2002 (vs.
Cresskill High School) and repeated in 2003 (vs.
James Caldwell High School) and 2006 (vs.
Hunterdon Central High School). The 2000 team won the Group III championship, topping Paramus Catholic High School, 15-8 and 15–7. The 2001 team repeated, defeating Ramapo High School in the finals. The girls took the title again in 2003, over cross-district rival
Northern Valley Regional High School at Old Tappan. The team took the 2006 Group II title over Chatham High School (25–17, 25–15). The 2001 team won the Group III state title over
New Jersey State Interscholastic Athletic Association and lost in the Tournament of Champions final match to
Immaculate Heart Academy, finishing the season with a 24–4 record. In 2012, the girls volleyball team won the state Group II championship in straight sets over Sterling High School, the program's eighth state group title. The boys' basketball team won the 2004 North I, Group III title, edging
Teaneck High School, 53–50. The boys swimming team won the Public C state championship in 2016–2019. Both swim teams won their respective North I Group B state titles in 2007, the girls defeating
Kinnelon High School 103–67 in the finals and the boys topping Ramapo High School 104–66. The 2016 boys' swimming team won the state Group C championship, the program's first state title, topping
Haddonfield Memorial High School 90–80 after going 13–0 in the season. In 2018, the school's Ultimate Frisbee team, The Northern Valley Coalition, were ranked 5th statewide. In 2019, the team won the Division II New Jersey state championship. ==Music department==