Brentwood School has a long tradition of athletic excellence, as Lady Eagle and Eagle teams have captured 17 state and 94 region championships since 1971. Brentwood is currently a member of Region 1-AA of the Georgia Independent Schools Association (GISA) Interscholastic division. The school fields varsity, junior varsity, middle school, and elementary teams in a wide range of athletic competitions throughout the year.
During the fall, the school fields teams at the varsity, junior varsity, and middle school levels in girls' fast-pitch softball; varsity and junior varsity teams in both girls' and boys' cross-country; varsity, middle school, and elementary school teams in football; and varsity and junior varsity squads in the sport of competitive cheerleading.
In the winter Brentwood teams compete at the varsity, junior varsity, and middle school levels in both girls' and boys' basketball. The school also offers an intramural basketball program for students in grades 3 through 6.
Spring is also a busy time of year, as Brentwood fields varsity, junior varsity, and middle school teams in baseball; varsity and junior varsity teams in both girls' and boys' track and field; varsity teams in both girls' and boys' tennis; and a varsity golf team. The school also made its first venture into the sport of soccer in the spring of 2009, when a large number of middle school students participated in an intramural soccer program. The school hopes that soccer will soon become an interscholastic activity at Brentwood.