The potential benefits of mindfulness–the cultivation of non-judgmental awareness and attention to the present moment–is an emerging field of inquiry for psychology and education researchers. Findings from a growing body of studies suggest that undertaking mindfulness-based breathing for a short time each day can mediate the impact of emotions in classroom events. We focus on ways in which two teachers and their students and the researchers developed emerging understandings of mindfulness during a three-month breathing intervention. Drawing on video data of the teachers leading classroom breathing sessions and associated conversations with teachers as well as a training session, we highlight some of the challenges encountered as teachers introduced mindfulness-based breathing in classroom settings.