This study aims to examine the effectiveness of a workplace-based intervention program to improve mental health, work ability, and work productivity in privately owned enterprises in China. A prospective cohort intervention study design was employed in which the intervention program was implemented for 30 months (from July 2009 to December 2012). Nine privately owned retail enterprises in China participated in the intervention study. Researchers administered a self-report survey to 2768 employees. The research team measured participants' job stress, resilience, work ability, absenteeism, depression, and work performance. A comprehensive Health Promotion Enterprise Program was implemented that entailed the following components: policies to support a healthy work environment, psychosocial interventions to promote mental health, provision of health services to people with mental illness, and professional skills training to deal with stress and build resilience. Analysis of variance was used to examine preintervention versus postintervention differences in stress, resilience, and work ability. Logistic regression was used to examine absenteeism related to depression. The results suggest that the intervention program was effective at improving participants' ability to work, their sense of control over their jobs, and, in particular, their ability to meet the mental demands of work. The intervention program also reduced participants' job stress levels and reduced the probability of absenteeism related to depression. The intervention programs incorporating both individual-level and organizational-level factors to promote mental health were effective and have implications for both practice and policy regarding enterprises taking more responsibility for the provision of mental health services to their employees.