This study evaluated the association between justice in the workplace (and other psychosocial factors) and mental health among healthcare professionals. It was conducted in a sample of hospital employees in Italy. The prevalence of mental disorders was assessed and the relationships between having a disorder and the level of perceived justice, job control and effort-reward imbalance were investigated. Psychiatric morbidity among professionals with higher perceived justice were 0.3–0.9 times lower than those among those with lower perceived justice. This finding suggests that improving fairness at work does matter for disease prevention and mental health promotion policy.