This research aims to explore if the implementation of a mindfulness based stress reduction (MBSR) intervention with teenage girls increases levels of mindfulness and well-being and decreases anxiety, as measured by the Mindfulness Attention Awareness Scale (MAAS), Warwick-Edinburgh Mental Well-being Scale (WEMWBS) and The Spence Children’s Anxiety Scale (SCAS), respectively. An exploratory mixed methods design was used, involving sequential data collection. Quantitative data was collected pre and post intervention, qualitative data was collected following the intervention and after the quantitative phase of the study was completed. Combining both qualitative and quantitative data provided a better understanding of intervention impact and generated a rich picture of both process and outcomes. The mindfulness intervention incorporated MBSR techniques and some exercises which were based on Biegel’s (2009) stress reduction workbook for teens. The key findings from this study indicate a significant difference on the students’ levels of mindfulness and well-being as measured by the MAAS and WEMWBS after the intervention took place. There were slight decreases on the SCAS scores however it was not significant. In the semi-structured interviews students highlighted a range of benefits from using mindfulness including: lower levels of stress, improved levels of concentration and attention and higher levels of self-esteem and self-efficacy. These findings are largely consistent with existing literature regarding the use of mindfulness with children and young people.