This research project aims to evaluate the effectiveness of a cognitive behavioral therapeutic (CBT) group in reducing self-stigma for people with mental illness in Chinese society. In this study, a quasi-experimental research method was adopted involving 71 people with mental illness receiving community-based mental health services. In total, 33 treatment group participants were assigned to a 10-session CBT group, while 38 control group participants received treatment as usual. Standardized assessment tools were used to collect data in the pre- and posttreatment periods by a research assistant. Analysis of covariance demonstrated that the CBT group was significantly more effective than the control group in terms of reducing self-stigma and depressive mood, with a moderate effect size, even after controlling for differences in various demographic variables between the treatment and control groups. This study provides evidence to support the efficacy and effectiveness of a CBT group for reducing self-stigma for people with mental illness.