The increased availability of nutritional supplements has been accompanied with concerns about safety and failed doping tests in athletes through contamination and presence of unknown ingredients. We sought to obtain baseline information on young athletes’ knowledge and practices regarding supplements which can guide development of educational programmes. Questionnaires were administered to Jamaican athletes aged 12–19 years attending after-school training for competitive events including the annual athletics competition- Girls and Boys Championship or “Champs”. The questionnaires comprised 27 questions divided into four sections: i) demographics, ii) supplement-taking habits iii) supplement perception and iv) knowledge. Of 127 athletes, the 57.4% (N = 73) that had taken supplements at least occasionally in the last year, had completed significantly more years of training,3.5 ± 1.5 versus 2.8 ± 1.2 years (± standard deviation), than non-users (P < 0.05) and those training for Champs were more likely to take supplements (P < 0.005). Males and Champs athletes were more likely to obtain supplements from coaches, and more likely to not know the source of the supplements compared with other athletes (P < 0.05 in all instances). 37.1% athletes stated they thought that supplements could increase sports performance. Knowledge was poor with average scores of 38% for the knowledge section with Champs athletes obtaining significantly lower scores than athletes partaking in other sports. Athletes with self-reported familiarity of the World Anti-doping Code obtained higher scores (P < 0.0005). The poor knowledge of supplement usage and of the World Anti-doping Code warrants training of students regarding the potential risks of taking supplements.