Background: From the perspective of achievement goal orientation theory, athletes may evaluate their performance by comparing current achievements with previous achievements (task orientation) or with those of other athletes (ego orientation); these two orientations may affect their sport motivation and performance outcomes in different ways. Objective: Based on a sample of competitive Czech beach volleyball players, this study aimed to assess the relationships among achievement goal orientations (task/ego), sport motivation (represented by intrinsic motivation, extrinsic regulation, and amotivation), and athletes' competitive performance. Methods: A total of 128 beach volleyball players (63 men and 65 women, age 26 ± 6.27 years, range 14-42 years) from the highest Czech national competition participated in the questionnaire survey. The questionnaire battery included the Sport Motivation Scale-6 as a measure of self-determined sport motivation and the Perception of Success Questionnaire as a measure of achievement goal orientation. We used multiple linear regression models to assess the relationships among achievement goal orientations, different types of sports motivation, and athletes' performance in sports competition measured by their point averages at the end of the season. Results: In regression models, we observed different effects of task and ego orientations on dependent variables, including intrinsic motivation, external regulation and athletes' competitive performance. Specifically, we found a highly significant effect of task orientation in the model of intrinsic motivation (ß = .522, p < .001, R 2 = .255) and a highly significant effect of ego orientation in the model of external regulation (ß = .394, p < .001, R 2 = .132). Furthermore, we found a significant effect of ego orientation in the model of athletes' competitive performance (ß = .239, p = .005, R 2 = .122). Conclusions: We assume that task and ego orientations contribute to different outcomes in competitive athletes, with task orientation supporting athletes' interest in and enjoyment of the sport and ego orientation supporting athletes' external regulation and performance in competition. Based on self-determination theory, task orientation may affect intrinsic motivation through the satisfaction of the basic needs of autonomy, relatedness and competence. At the same time, ego orientation may support less self-determined motivation but may also represent an advantage in the highly competitive environment of elite sports.