The Mustang Athletic teams compete in the Hacienda League of the CIF Southern Section offering 22 seasonal sports.

The Walnut High football team contends in Division 11 of CIF Southern Section.

[9] The Walnut High School Girls Golf Team won their first CIF State title in 2016.

[citation needed] The Lady Mustangs (Girls Soccer Team) won the CIFss in 2002, 2003, 2004.

[citation needed] Walnut Girls' Wrestling Team won CIF State Championship in 2024