© 2019 Elsevier Inc. Introduction: Stress negatively impacts pharmacy students' physical and mental health. Mindfulness has been shown to improve student wellbeing. The purpose of this study was to assess the feasibility and acceptability of an online mindfulness-based intervention and determine its effect on student wellbeing. Methods: A quasi-randomised controlled trial was conducted at four pharmacy schools in Ireland. The intervention group took part in a four-week online mindfulness course. The control group received usual education, with delayed access to the course. Participants completed the Perceived Stress Scale, the General Health Questionnaire, the Jefferson Scale of Empathy - Health Profession Student version, the Maslach Burnout Inventory Student Survey (MBI-SS), and the Five Facet Mindfulness Questionnaire at baseline and post-intervention. Answers provided to questions about the experience of participating in the course were analysed using thematic analysis. Results: Of the 52 participants, no significant differences were found between the intervention and control groups at baseline. Post-intervention, an increase in professional efficacy, as measured by the MBI-SS, was found in the intervention group (p = 0.004). There was also an increase in observing scores (p = 0.003). Males showed greater improvements in stress (p = 0.04) and non-judgement (p = 0.03) levels. Only females demonstrated improvement in professional efficacy (p = 0.002). Participants self-reported stress reduction and increased awareness of emotions. Conclusion: This study provides insights into the feasibility and acceptability of an online mindfulness course for pharmacy students. Findings will inform the future design and implementation of larger studies.