During adolescence, an adequate diet is needed to fuel performance and support growth and development. While many factors may impact dietary practices, there are some positive associations between nutritional knowledge (NK) and dietary intake. Understanding levels of NK is a key aspect in improving athletic performance. The aims of this research were to evaluate the NK of adolescent Ladies Gaelic Football (LGF) players and to determine whether there are any differences between age groups and between competitive level. One hundred seven LGF players completed the abridged Nutrition for Sport Knowledge questionnaire. Participants were between 16 and 18 years of age and of a highly trained and trained standard. Results showed overall “poor” levels of NK among the n = 107 participants. Scores for total, general, and sport NK were 43.5%, 56.8%, and 37.3%, respectively. Areas of NK that participants scored lowest on related to macronutrient requirements, refueling after exercise and supplement use. No significant differences were found for total, general, or sport NK based on age (16, 17, or 18 years) or playing level (highly trained vs. trained). NK levels among adolescent LGF Association players are “poor,” regardless of age, and playing level. This finding highlights the need to implement nutrition education with LGF Association adolescents to improve NK. Future research should adopt a longitudinal approach to evaluate the impact of nutritional education for adolescent female players.