TorontoChange
Brien McMahon High School's crosstown rival is Norwalk High School. The two schools compete in an annual Thanksgiving Day football game. The boy's lacrosse team was the Division 2 State Champions in 2000 and Division 1 runner-up in 2005. The football team was state champion in 1994. The girl's lacrosse team was Division 2 State Champion runner-up in 2007. Brien McMahon is a member of the FCIAC athletic conference. The Baseball team was Class LL State Champion runner-up in 2009 and was the FCIAC Central Division Champion in 1998 and 2006.
The school's marching band, also known as the Marching Senators, is known for their ability in competition. They perform several times each year in prestigious venues such as MetLife Stadium.
The Center for Global Studies is a magnet school within Brien McMahon High School. The center is a magnet program for high school students in Fairfield County that want to learn the Arabic, Chinese, or Japanese language and the respective culture and history. Beginning in Fall 2006 a Middle Eastern Studies program was introduced.