The nutrition knowledge of athletes and coaches is often inadequate. However, athletes need sufficient knowledge of this subject to understand the importance of food choices for their athletic performance, recovery, and overall health. Adequate nutrition knowledge and skills are important for coaches because they are often the most significant source of nutrition knowledge for their athletes. Most previous nutrition knowledge studies have been carried out in team sports and outside Scandinavia. The aim of this study, therefore, was to evaluate the nutrition knowledge of Finnish endurance athletes (156 males and 156 females; age = 17.9 ± 1.2 years) and their coaches (69 males and 25 females; age = 44.3 ± 12.3 years). The three main sports among the participants were cross-country skiing (n = 53 coaches and n = 111 athletes), orienteering (n = 13 and n = 110), and biathlon (n = 6 and n = 38). On average, the coaches (N = 94) answered 81% ± 9% of the 79 nutrition questionnaire items correctly, whereas the respective result was 73% ± 9% among the athletes (N = 312). The coaches had significantly (p < .001) better nutrition knowledge of all the five subcategories of the questionnaire, whereas the “dietary supplements” and “nutrition recommendations for endurance athletes” subcategories appeared particularly difficult for the athletes. The average nutrition knowledge score of athletes was relatively low. As nutrition knowledge may have a positive association with athletes’ food choices and subsequent dietary intake, Finnish endurance athletes and coaches would benefit from enhanced nutrition education.