Extensive research outlines a broad spectrum of physical and mental health benefits associated with participation in yoga. In particular, yoga can increase mindfulness as well as decrease anxiety, depression, and stress. However, knowledge of the underlying mechanisms and conditions for promoting positive outcomes requires further study. Limited research has examined how the quality of the relationship between the yoga student and instructor may influence potential health benefits derived from participation in yoga. The present study investigated associations between levels of stress, emotional well-being, motives for yoga, relationship quality, and mindfulness during yoga. Analysis of data collected from 219 adults indicated that higher levels of stress and negative emotional well-being increased the likelihood that yoga was practised to address psychological motives rather than perceived physical health benefits. Additionally, relationship quality with the instructor was found to predict greater state mindfulness during the yoga session. The present study highlights the importance of the relationship quality between instructor and student; future research investigating the efficacy of yoga in optimizing mental health should consider how health outcomes might be influenced by motives for participation and interpersonal relationships.