Objective: The objective of this study was to access the effect of athletes' attitudes, beliefs, and knowledge on doping and dietary supplementation in Saudi sports clubs so that the Saudi Arabian Anti-Doping Committee (SAADC) might be better prepared to address these issues with athletes. Methods: A cross-sectional prevalence type of study was conducted in Saudi sports clubs in six cities: Almadinah Almunawwarah, Jeddah, Abha, Tabuk, Dammam, and Riyadh. Athletes aged between 20 and 35 years were randomly selected by a systematic random sampling technique. We used a questionnaire that consisted of 55 questions divided into four categories: use of doping and dietary supplements, reason for consumption of doping and dietary supplements, personal beliefs about doping and dietary supplements, and behavior. Results: Of the 650 athletes surveyed, 155 were excluded due to incomplete data. The total number of completed questionnaires was 445 (68.5%). The survey results showed a high number of athletes reported that the main purpose of physical activity was for the health (n = 292; 65.6%), followed by to increase muscle size (n = 282; 63.5%), and weight loss (n = 100; 22.4%). Of the participants, 294 (66.1%) did not take dietary supplements, while 151 (33.9%) took supplements. Data also indicated that the highest percentage of respondents (n = 376; 84.5%) did not use doping, yet a small percentage (n = 33; 7.4%) still use doping. Conclusion: A majority of Saudi athletes in sports clubs indicated that the reason for their use of doping products and dietary supplements was to improve their health, increase muscle size, and improve their performance.