Stress has been reported among Swedish social workers for over a decade. Survey data from a longitudinal quasi-experimental trial in the public sector of reduced working hours, with a proportional decrease in workload and retained full pay, were used to examine the effect on stress, symptoms of Exhaustion syndrome, psychosocial work characteristics and work-life balance in social workers. Reduced working hours had a positive effect on restorative sleep, stress, memory difficulties, negative emotion, sleepiness, fatigue and exhaustion both on workdays and weekends; on sleep quality on weekends; and on demands, instrumental manager support and work intrusion on private life.