Background: The importance of junior doctor morale is increasingly being recognised. We aimed to identify and explore the factors affecting junior doctor morale in a UK teaching hospital., Methods: We carried out an online survey asking junior doctors to rate their morale, rank the top five factors that positively affected morale and offer free-text comments., Results: Nine hundred and forty three junior doctors were approached, 402 (42.6%) responded. Overall morale was rated 6 [interquartile range (IQR): 5-8], and how valued 6 (IQR: 4-8), supported 7 (IQR: 6-9) and autonomous 7 (IQR: 6-8) they felt [median ratings using a scale of 0 (low)-10 (high)]. When comparing the four domains of feeling supported, feeling valued, having autonomy and overall morale, respondents felt most supported overall (n = 402, χ2 = 85.6, p < 0.0001). Key themes were identified: team working and relationships, feedback, training and education, resources, wellbeing and pastoral support, staffing and workload, senior clinician support, and autonomy. The most common factors positively affecting morale were 'feeling part of a team' (66.4%) and 'being recognised for good practice' (56.7%)., Conclusion: We identified a number of diverse themes affecting junior doctor morale. Doctors felt more supported than valued or autonomous, with complex relationships between these domains., Competing Interests: RS was a Royal College of Physicians Chief Registrar at the time of undertaking this work. JSM is a Dunhill Medical Trust Research Training Fellow (RTF97/0117).