The purpose of this study was to provide an integrative review of ACT for mental health problems to identify content of program and discuss methodological strategy of intervention according to target population. According to Whittmore and Knaf's integrative review method, this research was conducted in five stages: clarification of research problems, literature search, and quality evaluation of data, data analysis, and data description. The key words in English and Korean were used to search through seven electronic databases. 21 studies were finally included in this integrative review. ACT was used as an intervention for anxiety, depression, posttraumatic stress disorder and eating disorders and was effective in social avoidance, anxiety sensitivity, depression, dysfunctional belief and negative thinking. It was also used as an intervention for the maladjustment in adolescence to improve self-esteem and reduce behavioral problem. The six core processes of ACT are useful for people with chronic mental illness who have an ineffective avoidance strategy that avoids their symptoms and does not accept the illness. We give a suggestion that researchers develop and apply appropriate ACT for mentally ill person in hospitals.