Assertive Community Treatment (ACT) is an outreach-based case management model that assists people with severe mental illness through an intensive and integrated approach. In this program, a multidisciplinary team provides medical and psychosocial services. The purpose of this study was to examine the effectiveness of the following two ACT intervention strategies: "replacement" (supporting the clients) versus "backup" (supporting family members who provide care to clients). Admission days, psychiatric symptoms, quality of life, self-efficacy, and service satisfaction ware evaluated as outcome variables. To identify effective methods of supporting family members, clients living with family were divided into two groups based on the amount and types of services received-the backup group and the replacement group. ANCOVA was used to compare the outcomes between the two groups. The replacement group displayed significantly better psychiatric symptoms, social functioning, self-efficacy, and service satisfaction scores. No differences in admission days or quality of life were found. Clients provided more support directly to clients themselves than to family members was found to have better client outcomes in improving psychiatric symptoms, social functioning, and self-efficacy, resulting in higher levels of service satisfaction. This indicates that society should reduce the responsibility of the family and share responsibility for the care of people with mental illness to effectively improve outcomes for people with mental illnesses.