Acceptance and commitment therapy (ACT) has substantial support in adult populations but less among adolescents. To date, very little research has evaluated whether it can be delivered in a highly accessible school context. This study examined a 6-hour, weekly ACT-informed school-based group intervention for adolescent girls, focusing on anxiety, depression and building psychological flexibility. Participants (N = 10) who completed the intervention experienced significantly lowered levels of anxiety and increased psychological flexibility, with postintervention scores for all variables trending in the expected directions. Findings provide preliminary support for the efficacy of the intervention and encourages further evaluation of ACT delivered in schools.