Background: Doctors’ organisations in the UK have reported worrying levels of work-related stress and burnout in the general practitioner (GP) workforce for some time, and the COVID-19 pandemic has presented clear new challenges. Aims: To synthesise international evidence exploring the impact of COVID-19 on primary care doctors’ mental health and wellbeing and identify risk factors associated with their psychological wellbeing during this time. Design and setting: Mixed-methods systematic review. Method: We searched six bibliographic databases, Google Scholar and MedRxiv and conducted reference checking to identify studies of GP psychological wellbeing during the pandemic. Two reviewers selected studies, extracted data and assessed the quality of studies using standardised tools. Heterogeneity in outcomes, setting and design prohibited statistical pooling; we combined the studies using a convergent integrated thematic synthesis. Results: Thirty-one studies were included. Multiple sources of stress were identified, including changed working practices, risk, exposure and inadequate PPE, information overload, pandemic preparedness and cohesion across sectors. Studies demonstrated an impact on psychological wellbeing, with some GPs experiencing stress, burnout, anxiety, depression, fear of COVID, lower job satisfaction and physical symptoms. Studies described gender and age differences: women report poorer psychological outcomes across all domains and older GPs reported greater stress and burnout. Use of outcome measures and reporting practice varied greatly. Conclusion: Our review of international evidence demonstrates that the COVID-19 pandemic has adversely affected GPs’ wellbeing around the world. Further research could explore gender and age differences, identifying interventions targeted to these groups.