Background Dietary supplements are commonly utilized worldwide, including in the Kingdom of Saudi Arabia (KSA), primarily to improve memory, focus, wakefulness, learning, and academic achievement. Nevertheless, there is still uncertainty regarding their efficacy and safety, particularly concerning academic performance. This study examines the prevalence of dietary supplement use among students in KSA and how this affects their academic performance. Methodology The current study was a cross-sectional study conducted in KSA between 2022 and 2024 on a sample size of 513 students aged ≥18 years, as calculated by Epi Info software (Centers for Disease Control and Prevention, Atlanta, United States). A self-administered online questionnaire was designed, tested for validity and reliability, and then propagated via social media. It included four parts assessing the socio-demographic, past medical and medication history, academic information, and dietary supplement use. Results The results showed that 360 (70.2%) participants used dietary supplements, while most of them, 141 (39.2%), used a combination of supplements. Users who reported taking supplements every day were 266 (73.9% of supplement users), and the supplement-related adverse effects occurred in about 147 (41% of supplement users). The most commonly reported side effects were headaches, sleeplessness, and irritability. No discernible influence of any of the reported dietary supplements on academic achievement was identified, despite the high prevalence of supplement usage and the related negative effects. A high percentage of the participants had incorrect knowledge about dietary supplements - 262 (51.1%) had a false belief that supplements can improve their achievement and 238 (46.4%) considered them completely safe with no risks of adverse effects. Conclusions Nutritional supplement intake was highly prevalent among KSA students
however, no positive association was identified between academic achievement and any of the used supplements (caffeine, creatine, curcumin, omega-3 fatty acids,