[Purpose] This study aimed to examine the validity and internal consistency of the Japanese version of a performance evaluation tool for activities of daily living (ADL) based on the modified Barthel Index (PET-MBI) among elderly people at home. [Subjects] The subjects were elderly people living at home in Japan. [Methods] A cross-sectional study was performed at five home care facilities for elderly people in Japan. ADL performance was evaluated for 128 participants using the PET-MBI, which included 10 self-care items. We used confirmatory factor analysis to estimate the factorial validity. We assessed data model fitness with the χ² statistic, the Goodness of Fit Index (GFI), Adjusted Goodness of Fit Index (AGFI), and Root Mean Square Error of Approximation (RMSEA). Cronbach’s alpha coefficient was used to determine the internal consistency. [Results] The mean age of the participants was 79.1±8.9 years. Among the 126 participants included in the analysis, 67 were women (53.2%). The single-factor model demonstrated a fair fit to the data, with the χ² statistic = 74.9 (df =35), GFI = 0.88, AGFI = 0.81, and RMSEA = 0.096, and the path coefficients of each item ranged from 0.44 to 0.95. The alpha coefficient of the 10-item scale was 0.93. [Conclusion] The PET-MBI for elderly people at home was well validated.