Background: Medical student mental health and wellbeing is highly topical and the subject of much research. While theoretically informed definitions of wellbeing abound, how do medical students themselves understand and perceive wellbeing? What aspects of the curriculum do they regard as affecting their wellbeing and mental health? This study explored these questions, and aimed to identify factors associated with student acceptability of wellbeing programs and interventions. Methods: All students at an Australian undergraduate medical school (n = 619) were invited to complete a qualitative online questionnaire between 2017 and 2018 following the introduction of several wellbeing initiatives, including "Wellbeing Days" (WBD). WBD allow students to take single absence days for self-care. Open-ended questions were asked about perceptions and experience of mental health and wellbeing, and views on interventions to improve wellbeing such as WBD. Thematic analysis was conducted across all responses. Three authors developed preliminary themes, which were then refined and confirmed by all researchers. Thematic saturation was achieved within data from the 68 respondents, which included participants from all cohorts. Results: Participants described wellbeing as positively experienced work/life balance, impacted by four factors; contact hours, peer relationships, staff relationships, and trust in how wellbeing initiatives were used. Long contact hours were deemed incompatible with self-care activities, maintaining employment, and seeking professional medical/psychological help. Peers could promote wellbeing by offering social and academic support, but also undermine wellbeing by being competitors. Degree of trust, engagement and communication with staff influenced acceptability of interventions. Participants viewed initiatives such as WBD favourably, but distrust of peers, and of staff, led to perceptions that WBD could be prone to misuse, or used for surveillance rather than support. Conclusion: Our findings suggest that wellbeing days which allow self-care, reduction in contact hours, and peer support may promote student wellbeing, but the acceptability of any interventions is influenced by relationships between staff and students, and in particular, trust in these relationships. We suggest strategies to strengthen trust and further research to investigate the relationship between trust and perceptions of wellbeing in self and peers.