BACKGROUND: International mobility of health workforce affects the performance of health systems and has major relevance in human resources for health policy and planning. To date, there has been little research exploring the reasons why general practitioners (GPs) migrate. This mixed methods study aimed to investigate the reasons why Spain-trained GPs migrate and develop GP retention and recruitment health policy recommendations relevant to Spanish primary care. METHODS: The study followed an explanatory sequential mixed methods study design combining surveys with semi-structured interviews and focus groups with GPs who qualified in Spain and were living overseas at the time of the study. The survey data examined the reasons why GPs left Spain and their intention to return and were analysed using quantitative methods. The transcripts from interviews and focus groups centred on GPs' insights to enhance retention and recruitment in Spain and were analysed thematically. RESULTS: The survey had 158 respondents with an estimated 25.4% response rate. Insufficient salary (75.3%), job insecurity and temporality (67.7%), excessive workload (67.7%), poor primary care governance (55.7%), lack of flexibility in the workplace (43.7%) and personal circumstances (43.7%) were the main reasons for leaving Spain. Almost half of the respondents (48.7%) would consider returning to Spanish general practice if their working conditions improved. Interviews and focus groups with respondents (n = 24) pointed towards the need to improve the quality of employment contracts, working conditions, opportunities for professional development, and governance in primary care for effective retention and recruitment. CONCLUSION: Efforts to improve GP retention and recruitment in Spain should focus on salary, job security, flexibility, protected workload, professional development, and governance. We draw ten GP retention and recruitment recommendations expected to inform urgent policy action to tackle existing and predicted GP shortages in Spanish primary care.