© 2017 Association for Child and Adolescent Mental Health Background: Group Mindfulness Therapy (GMT) is a program tailored for adolescents that targets anxiety with mindfulness skills including present moment awareness, mindfulness in everyday life (breathing, eating, walking), body scan, loving-kindness, and self-acceptance. Youth with anxiety may benefit from mindfulness exercises precisely because they learn to redirect their mind, and presumably their attention, away from wandering in the direction of worry and negative self-appraisals and toward greater acceptance of internal states. This open trial assessed the feasibility and initial effectiveness of GMT in a school setting. Method: Twelve 6th and 7th grade adolescents with elevated anxiety [Screen for Child Anxiety Disorders (SCARED) ≥ 30] participated in GMT after school. Youth completed measures of anxiety and perceived stress and their parents completed measures of internalizing and externalizing behavior problems at pretreatment and posttreatment. We hypothesized that GMT would significantly reduce youth anxiety and stress. Results: Significant improvements were observed in anxiety, internalizing, stress, and attention, with effect sizes ranging from.88 to 1.34. Conclusions: We demonstrate that GMT is feasible and acceptable to adolescents presenting with anxiety as a primary concern. We provide further support for the use of a mindfulness-based intervention for anxiety reduction. The group format suggests a cost-effective way to deliver services in a school setting.