AIM: The critical role of nutrition in athletes’ performance is widely accepted, and water polo players are no exception. However, there are no studies about their adequate knowledge of proper nutrition. Thus, the purpose of this study was to assess the nutritional knowledge of water polo players. MATERIAL & METHOD: We examined 30 male and 11 female water polo players of the A1 Greek national league, aged 16-37. Participants answered the “General Nutrition Knowledge Questionnaire” (Kliemann et al., Eur J ClinNutr 70: 1174–1180, 2016) consisting of 86 questions on general nutrition knowledge. Results were analyzed with descriptive statistics and with the χ2 test to examine gender differences. RESULTS: Participants answered correctly 59% and incorrectly 41% of the questions. The majority of false answers were about the role of fruits and vegetables, body composition, fats, nutritional supplements, salt, the energy content of food, micronutrients, sugar-containing foods, alcohol, the glycemic index, and whole-grain foods. Males performed significantly better in 2 questions compared to females (which combination of vegetables had more vitamins and which of chip choices is lower in fat). CONCLUSIONS: Water polo players had satisfactory knowledge on general nutrition, with males performing slightly better than females. However, they should receive further education on nutrition by experts in order to clarify misconceptions that still exist.