Objective: To assess the associations between psychological factors and return to work among long-term sickness absentees. Design: Longitudinal study with a 3-year follow-up. Subjects: Long-term sickness absentees (n = 905) who had undergone a multidisciplinary medical assessment. Methods: Three years after multidisciplinary medical assessment, return to work status (full, partial, or none) was determined according to whether the individuals received full, partial, or no sickness benefits. Multinomial logistic regression analyses were performed to assess the odds ratios with 95% confidence intervals for return to work related to indecision, lassitude, fatigability, reduced sleep, social functioning, emotional role limitations, and vitality. Results: After adjusting for socio-demographic factors and medical diagnoses most of the studied psychological factors were significantly associated with full (odds ratios 2.13-1.50) and partial (odds ratios 2.25-1.63) return to work in the follow-up period. Low level of lassitude was associated with full return to work (odds ratio 1.72) even when the other psychological factors were controlled for. Similarly, low fatigability was associated with partial return to work (odds ratio 1.81). Conclusion: This study indicates that psychological factors are important for both full and partial return to work among long-term sickness absentees who have undergone a multidisciplinary medical assessment.