The Saddle River Day School Rebels participate in the
North Jersey Interscholastic Conference, which is comprised of small-enrollment schools in Bergen,
Hudson,
Morris and
Passaic counties, and was created following a reorganization of sports leagues in Northern New Jersey by the
New Jersey State Interscholastic Athletic Association (NJSIAA). Previously, the school was a member of the all-private Patriot Conference, but after a decision by the NJSIAA in February 2008, both
Hawthorne Christian Academy and Saddle River Day School joined the Olympic Division of the
Bergen County Scholastic League (BCSL) later that year, and remained in the conference until it was disbanded as part of the NJSIAA's 2010 realignment. The BCSL was disbanded as a part of a wide-ranging realignment of high school sports in northern New Jersey, and Saddle River Day moved to the new NJIC in the fall of 2010. With 133 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 II for public schools). The girls basketball team won the Non-Public Group B state title in 2018 (defeating
Rutgers Preparatory School in the tournament final) and 2019 (vs.
Trenton Catholic Academy), and was declared as the Non-Public North B sectional champion in 2020 after finals were cancelled due to COVID-19. The team won their first title with a 73-49 win against Rutgers Prep in the finals of the Non-Public B tournament final. The 2019 team repeated as winner of the Non-Public B title against Trenton Catholic by a score of 79-67 in the title game. The teams advanced to the
Tournament of Champions both seasons. In 2018, the team was the fifth seed, winning the quarterfinals by 92-63 against fourth-seeded
University High School before losing to number-one seed
Manasquan High School 80-67 in the semifinal game played at the
RWJBarnabas Health Arena to finish at 24-7 for the season. The 2019 team was the second seed and won the semifinal round by a score of 76-63 against number-three seed
Manchester Township High School before losing in the finals to top seed
Franklin High School by a score of 65-57 and finishing the season at 28-3. ==Notable alumni==