Brooke Diamond O'Brien '03 joined the women's lacrosse staff as the head coach in the summer of 2022. The 2025 season is her third season with the Mammoths.
In her two seasons, O'Brien coached the Mammoths to a 17-14 combined record, reaching the NESCAC Quarterfinals twice. She has seen five players named to All-NESCAC teams, with Colleen Mooney '23 earning First Team honors in 2023 and Mia Raven '27 winning NESCAC Rookie of the Year in 2024. She has seen her players succeed in the classroom, with the 2024 team earning being named an Academic Honor Squad, with 11 student-athletes garnering IWLCA Division III Academic Honor Roll selections.
O'Brien returns to Amherst after spending the previous 15 years as the head coach of women's lacrosse at Washington & Lee University, where she compiled a 221-60 (.786 win percentage) mark and was named conference coach of the year nine times. She guided the Generals to a 19-3 mark in 2022, a conference championship and a spot in the NCAA Div. III Tournament quarterfinals.
A native of Longmeadow, Mass., and an alumnus of the Loomis Chaffee School in Windsor, Conn., O'Brien graduated Magna Cum Laude from Amherst in 2003 with a bachelor of arts in psychology and law, jurisprudence and social thought. She earned a total of 12 letters as a member of the women's lacrosse, women's soccer and women's basketball teams and served as a captain for all three sports.
In lacrosse, she was a two-time First Team All-America selection and two-time Kelly Award winner as the Division III National Goaltender of the Year. She was named the Intercollegiate Women's Lacrosse Coaches Association (IWLCA) Division III Scholar-Athlete of the Year and was selected the Division III Women's Lacrosse Tournament's Most Outstanding Player in leading the then Lord Jeffs to the 2003 National Championship.
O'Brien's coaching career began at Amherst in 2005 as a graduate assistant women's lacrosse coach and she also coached at Smith College until 2007.
At Amherst, O'Brien assisted in all aspects of the program and helped lead the then Lord Jeffs to a No. 6 ranking and the NCAA Quarterfinals in 2006. At Smith, O'Brien coached the women's soccer team as an assistant and helped guide it to a 14-7-1 record and an ECAC New England Championship during the 2006 season.
