Summary The objectives of this study were to estimate the prevalence of burnout syndrome in a sample of Spanish social workers and analyse the influence of a series of socio-demographic variables that may potentially be related to the appearance and development of one of the three dimensions of burnout. A total of 947 Spanish social workers participated in the study. Findings 33.2% and 22.1 of Spanish social workers experienced high levels of emotional exhaustion and depersonalisation, and 54.2% experienced low personal accomplishment at work. The hierarchical regression analysis showed that having been on sick leave in the preceding year was the most important predictor of emotional exhaustion. Moreover, full-time employment status was the most robust predictor of depersonalisation, and professional activity in specialised social services was the main predictor of personal accomplishment. The low percentages of total variance explained imply that although certain socio-demographic characteristics are significant predictors, their effects are very small. Applications Public and private organisations devoted to social services should be aware of the need to prevent this type of psychosocial risk to which social workers are exposed every day. This would help improve the health and quality of their lives as well as reduce the high costs which frequent worker turnover and sick leave entail, and would also enhance the effectiveness of the services provided.