Nutrition intake plays a crucial role in improving athletic performance, enhancing adaptations to training, and augmenting recovery from exercise. However, research has reported that Gaelic footballers consistently fail to meet energy and carbohydrate recommendations. Sports nutrition knowledge (SNK) can influence the dietary intake of athletes, and therefore has the potential to have a significant impact on athletic performance. The aim of this study was to investigate the current level of SNK in elite Gaelic footballers (n = 100). An online version of the Nutrition for Sport Knowledge Questionnaire (NSKQ) was used to assess sports SNK. The overall mean SNK scores for Gaelic footballers and practitioners were 47.6 ± 12.3% and 78.1 ± 8.3%, respectively. There were no differences in knowledge between age groups, education level or divisional status. The top three sources of nutrition information identified by participants were team dietitian/nutritionists (84.0%), athletic trainers/strength and conditioning coaches (73%), and social media (37%). The results show that there is a major gap in the SNK of Gaelic footballers, while practitioners demonstrated a promising SNK, that could support Gaelic footballers. There is a need for development of interventions and knowledge transfer partnerships, including more effective methods of educating Gaelic footballers and translating sports nutrition principles to players. Developing appropriate nutritional education strategies using online resources and mobile applications could help to improve nutritional knowledge and practice of Gaelic footballers.