Abstract Objective: To assess the influence of the pain locus of control on return to work in fibromyalgia patients. Methods: Ninety-eight fibromyalgia patients on sick leave were enrolled in a multidisciplinary treatment program and were followed up for 12 months post-discharge. Treatment was considered successful at discharge in the case of patients who returned to work and unsuccessful in patients who remained sick listed. Treatment was considered successful during follow-up in patients who remained at work for at least the last 6 months of follow-up. Patients who took sick leave again and those lost to follow-up were considered failures. Logistic regression methods were used to define the best predictive models of treatment failure. Results: Fifty-eight patients were considered treatment successes at discharge and 50 at 12-month follow-up. The subscale Fate from the Multidimensional Health Locus of Control-Pain Scale and the Health Assessment Questionnaire predicted treatment failure at discharge (−2lnR=57.79; chi-square=74.74; df=2; Pb.001). The predictive model of treatment failure at 12-month follow-up was unspecific. Conclusion: Fibromyalgia patients undergoing a multidisciplinary treatment who were least likely to return to work at discharge were those with a pain locus of control characterized by more negative expectations about pain progression and a high perceived functional disability