Herbal supplements are widely consumed by athletes, but the underlying factors for this practice are not fully understood. This study aimed to adapt and validate a questionnaire to determine factors influencing consumption of herbal supplements among university athletes by integrating the Knowledge, Attitudes, and Practices (KAP) and Health Belief Model (HBM). The development of the initial set of survey questions, which includes KAP and HBM constructs related to herbal supplement consumption, was guided by a thorough review of existing literature and consultations with experts. The questionnaire was developed with seven constructs and 30 items (5 knowledge, 5 attitude, 5 perceived benefits, 6 perceived barriers, 3 self-efficacy, 5 practice and 1 cues to action). Content validity and face validity of the questionnaire were determined by 7 experts (CVI = 0.9) and 30 university athletes, respectively. A test–retest reliability (n = 38) was conducted (r = 0.982, p = 0.03). The construct validity was evaluated using exploratory factor analysis (EFA) on data collected. The Kaiser–Meyer–Olkin measure of sampling adequacy (KMO) was 0.797. The Cronbach’s alpha for reliability of the knowledge, attitude, perceived benefits, perceived barriers, self-efficacy domains all showed acceptable values of > 0.8 (0.872, 0.840, 0.841, 0.830 and 0.889). This study successfully validated an instrument integrating KAP and HBM models for a comprehensive assessment of factors influencing herbal supplement consumption among university athletes. This validated instrument offers a valuable tool for future research to investigate the multifaceted influences on this behavior consuming herbal supplements.