Background: Diet impacts both human and environmental health and must be designed to optimize the training and performance of athletes. The aim of this study was to quantify the effect of dietary advice (DA) on the food intake of wheelchair basketball athletes (WBA) and the environmental impact longitudinally. Methods: DA were provided to WBA of the Italian national team (DAM-T1). Nutritional assessment and evaluation of the environmental impact of diet were performed two months (DAM-T2) and one year later (DAM-T3), when a post-COVID-19 survey was performed also in WBA who did not receive counselling (men: NDAM-T3, women: NDAW-T3). Results: After DA, WBA showed a reduced percentage of energy derived from sugars and fats. Athletes adjusted their protein intake according to the personalized recommendations. The intake of some micronutrients improved after DA and was higher compared to NDAM-T3 and NDAW-T3. Despite the lower impact of diet in NDAW-T3, they presented more nutritional deficiency than men. The mean intake of vegetables was in the range of the EAT-Lancet Commission suggestion only two months after DA. After DA, fiber intake increased and adapted to the tolerated level. Conclusions: WBA improved their diet after DA but did not comply with the EAT-Lancet suggestion for red meat and legumes.