Objective To translate the mentor competency assessment (MCA) into Mandarin, and test its reliability and validity. Methods Brislin translation model was used for translation and reverse-translation. The preliminary translation was culturally adjusted through expert committee discussions followed by a pre-tests. Mentors of clinical post-doctoral trainees at Peking Union Medical College Hospital (PUMCH) were enrolled as the survey subjects (n=153) from January 2020 to March 2020. General questionnaire and Mandarin version of MCA were used. Item analysis, reliability, and validity analysis of the Mandarin version of MCA were tested. Results The Mandarin version of MCA includes 26 items in six dimensions, including effective communication, establishing consistent expectations and goals, evaluating students, fostering independence, respecting diversity, and promoting students' professional development. Reliability analysis showed that Cronbach's coefficient score was 0.975, and split-half coefficient score was 0.951. Each item was positively correlated with the total score (r=0.634~0.823). The item content validity index (I-CVI) is 0.6~1.0, and the scale content validity index (S-CVI) was 0.954. The confirmatory factor analysis results showed that the ratio of χ² degrees of freedom (χ² /DF) was 1.865, the comparative fit index was 0.925, the Tucker-Lewis index (TLI) =0.914, and the standardized root mean square residual(SRMR)=0.043, and the root mean square error of approximation (RMSEA)=0.085 (95%CI,0.073~0.096,P<0.01). Conclusions The reliability and validity of the Mandarin version of MCA was evaluated and the Mandarin version of MCA is competent to the evaluation of the mentor competency of clinical and translational research mentors in China.