The Self-Identified Stage of Recovery (SISR) is a two-part scale assessing both the stage of recovery (SISR-A) and the component processes of recovery (SISR-B) for people with mental illness. This study aimed to develop a Japanese version of the SISR and to examine its reliability and validity. The Japanese versions of the SISR-A and SISR-B were developed through focus group cognitive interviews and the translation–back translation procedure. A cross-sectional questionnaire survey was conducted of 223 participants who had long term mental illness, were aged 20 years or older, and currently living in communities and inpatient ward settings; 59.2% were males and the average age was 47.6 years. The questionnaire also included the 24-item Recovery Assessment Scale, Herth Hope Index, Empowerment Scale, and Resilience Scale. Cronbach's alpha coefficient, intraclass correlation coefficient, and weighted kappas were generally fair to high, and the SISR-A and SISR-B scores were positively correlated with other relevant scales. This study supported the reliability and validity of the Japanese versions of the SISR-A and SISR-B among people with long term mental illness in Japan.