Objective <p>The Mental Health First Aid Knowledge Questionnaire (MHFAKQ) is a tool used in English-speaking countries for assessing the levels of knowledge about how to support individuals with mental health problems among non-mental health professionals. This study aimed to evaluate the reliability and validity of the MHFAKQ among Chinese non-mental health nurses.</p> Methods <p>Following the Sousa Translation Model (or the best practices in cross-cultural adaptation of research instruments), the MHFAKQ was translated into Chinese, back-translated, culturally adapted, and pre-tested. The instrument in the Chinese language was tested among a convenience sample of non-mental health nurses (<i>n</i> = 425) from a non-psychiatric department of a general hospital in China. Internal consistency and test–retest reliability were assessed by Cronbach’s alpha and intraclass correlation coefficient (ICC), respectively. Validity was evaluated using scale content validity and structural validity tests.</p> Results <p>The Chinese version of the MHFAKQ comprised 16 items within a single dimension. The content validity index (I-CVI) for individual items ranged from 0.875 to 1.000, with an average content validity index (S-CVI) of 0.992. Exploratory factor analysis identified one factor with an eigenvalue of 8.367, explaining 52.29% of the variance. The questionnaire demonstrated excellent internal consistency (Cronbach’s α = 0.939), test-retest reliability (0.822), and split-half reliability (0.940).</p> Conclusion <p>The Chinese version of the MHFAKQ shows reasonable reliability and validity to be applied among Chinese non-mental health nurses.</p>