BackgroundProper nutrition is vital in promoting community health, yet insufficient knowledge and improper dietary practices can lead to deficiencies and diseases. Professional athletes depend on optimal nutrition for their performance and recovery, but a lack of understanding can impede their potential. The nutritional status of athletes impacts their overall health and sports performance. Inadequate sports nutrition knowledge may result in suboptimal practices, reducing strength, power, endurance, and immunity. Additionally, disordered attitudes can lead to dietary imbalances and an increased risk of injury. This study, conducted in Qazvin, Iran, examined athletes’ nutritional knowledge, attitudes, and practices. By addressing these factors, there is potential to enhance dietary behaviors and ultimately improve athletes’ performance.MethodsThe study employed a descriptive-analytical, cross-sectional design to investigate the nutritional knowledge, attitude, and practice (KAP) of professional athletes in Qazvin, Iran. A total of 320 purposefully selected professional athletes (68.13% male, 31.87% female) from various sports fields participated in the research. The data collection tool consisted of demographic questions and a KAP questionnaire, including 27 nutritional knowledge questions, 16 nutritional attitude questions, and 14 nutritional performance questions. The quota sampling method was used to estimate sample sizes. Data analysis was carried out by SPSS v.26 using one sample t-test, one-way ANOVA, and Pearson’s correlation coefficient test.ResultsThe results showed that nutritional knowledge (the mean value was 79.594 ± 7.015 - the optimal knowledge level = 84) and attitude (the mean value was 23.347 ± 5.300 - the optimal attitude level = 26) for athletes are low, but their nutritional practice (the mean value was 21.788 ± 3.450 - the optimal performance level = 24) was moderate. Also, professional athletes’ nutritional knowledge, attitude, and practice were lower than normal (p < 0.05). Significant positive correlations were among knowledge, attitude, and practice (p < 0.05). However, there were no significant differences in nutritional knowledge, attitude, and practice among the subjects of different age groups, genders, and sports types (p > 0.05).ConclusionThis study showed that the nutritional knowledge, attitude, and practice of professional Iranian athletes in Qazvin province were low; therefore, the implementation of more theoretical and applied nutrition education, such as using knowledge assessment tools and interventions, irrespective of their age, sport’s field, and gender, is compelling.