Background Burnout and workforce shortages comprise a vicious cycle in medicine, particularly for Australian general practitioners (GPs). Professional diversification, whereby individuals work multiple roles across their week, may help address this problem, but this strategy is under-studied. Methods We surveyed 1157 Australian GPs using qualitative and quantitative questions examining professional diversification, values, autonomy, and wellbeing. Quantitative data were analysed using inferential statistics, whilst qualitative data were analysed using inductive thematic analysis. We triangulated the data by using the qualitative findings to inform further quantitative testing. Results Approximately 40% of the sample had diversified. Although diversifying was not significantly associated with wellbeing, the qualitative data indicated that diversification supported GPs’ wellbeing by enhancing career sustainability, accomplished through various pathways (e.g. value fulfilment, autonomy, variety). Subsequent quantitative analyses provided evidence that these pathways mediated the relationship between diversification and wellbeing. To diversify, GPs needed particular personal qualities, external supports, flexibility, and serendipity. Barriers to diversifying mirrored these factors, spanning individual (e.g. skillset) and situational levels (e.g. autonomy, location). Conclusions Diversification can support GPs’ wellbeing if it meets their needs. Organisations should focus on publicising opportunities and accommodating requests to diversify.