Psychological detachment from work, an off-job experience of "switching off" mentally, seems to be crucial for promoting employee's well-being. Previous studies on predictors of psychological detachment mainly focused on job-related factors, and only a few studies focused on family-related and personal factors. This study focuses not only on job-related factors (job demands, job control, workplace support) but also on family-related (family/friend support) and personal factors (workaholism), and examines the relation of these three factors with psychological detachment. Data of 2,520 Japanese employees was randomly split into two groups and then analyzed using cross-validation. Hierarchical multiple regression analyses revealed that family/friend support had a positive association with psychological detachment, whereas a subscale of workaholism (i.e. working compulsively) had negative associations with it across the two groups. Results suggest that family/friend support would facilitate psychological detachment whereas workaholism would inhibit it. © 2014 National Institute of Occupational Safety and Health.