The objective of the present study was to explore associations between psychosocial workload and mental health complaints in different age groups. A questionnaire was sent to 2021 employees of a Dutch railway company. Six aspects of psychosocial workload (work pressure, mental workload, emotional workload, autonomy, social support from colleagues and social support from supervisors) and three mental health outcomes (work-related fatigue, stress and burnout) were assessed. Associations between the aspects of psychosocial workload (distributed into tertiles) and health complaints were analysed by logistic regression analysis in four age groups (22-35, 36-45, 46-55 and 56-66 years old). In all age groups, worse work pressure was a significant risk factor for having mental health complaints. Worse emotional load in the younger employees and lack of social support in older employees were associated with a higher risk of having mental health complaints. Age-specific preventive measures should be implemented on both individual and group levels. STATEMENT OF RELEVANCE: With an ageing workforce, understanding relationships between age and work-related health ailments is increasingly important. This study found that emotional workload in younger and lack of social support in older employees were associated with a higher risk of mental health complaints. Work pressure was a risk factor in all age groups.