Background: Mindfulness-based interventions such as Mindfulness-based Stress Reduction (MBSR) and Mindfulness Cognitive Behavior Therapy (MCBT) have been used to treat adults with psychiatric disorders. This article describes initial modification and development of a mindfulness-based intervention group program for adolescents with psychiatric disorders. It was hypothesized that the intervention would improve mindfulness, mental health outcomes and decrease psychological distress and symptoms. Method: Adolescents from a mental health clinic attended a 5-week group pilot mindfulness-based intervention. Adolescents and parents completed questionnaires at pre- and post-intervention and at 3-month follow-up. Baseline measures indicated moderate to severe range of mental health symptoms. Results: After the intervention, adolescents reported significant decreases in psychological distress and increases in mindfulness and self-esteem. Qualitative data revealed the intervention to be engaging and beneficial. Parents also reported significant overall improvements of adolescents’ functioning. Conclusions: These promising preliminary results suggest that the intervention was feasible, acceptable and offered positive impact on mental health problems, and the intervention warrants further research in a randomized controlled study.