Purpose: This study aims to translate and test the reliability and validity of the Internalized Stigma of Mental Illness-Cantonese (ISMI-C). Methods: The original English version of ISMI is translated into the ISMI-C by going through forward and backward translation procedure. A cross-sectional research design is adopted that involved 295 participants randomly drawn from a population of Chinese consumers participated in different kinds of community-based mental health services. Results: Results show that the Cronbach's a coefficient of the ISMI-C is 0.93. With regard to validity test, the ISMI-C shows significant and negative correlation with measures on self-esteem and quality of life. Also, an explorative factor analysis yields five factors that are consistent with previous research results. Discussion: This study shows that the ISMI-C is a reliable and valid measure. ISMI-C can facilitate the development of interventions in reducing self-stigma for people with mental illness across Chinese societies.