Objective Mindfulness‐based interventions have enjoyed a marked increase in support within biomedical and psychological research and practice in the past two decades. Despite the widespread application of these treatments for a range of psychological and medical conditions, there remains a lack of consensus regarding mechanisms through which these interventions effect change. One plausible yet underexplored mechanism is the therapeutic alliance between participants and mindfulness instructors. Methods In this report, data are presented on therapeutic alliance from the mindfulness arm (n = 37) of a randomized controlled trial of a mindfulness‐based smoking cessation treatment. Results Results suggest that client‐reported therapeutic alliance measured midtreatment did not significantly predict primary smoking outcomes. Alliance did predict improvement in posttreatment scores on several outcome variables linked to mindfulness practice, including emotion regulation (β = −.24, p = .042), mindfulness (β = .33, p = .007), negative affect (β = −.33, p = .040), as well as treatment compliance (β = .39, p = .011). Conclusion Implications of these relationships and the possible role of therapeutic alliance in mindfulness treatments are explored.