Motivations to run marathons have been recognised by many researchers, but few have paid attention to triathletes. Mass triathlon participation is a new trend, which manifests itself as a human need to invoke strong emotions and seek them in difficult sports, as well as to travel to participate in such events. Therefore, the main goal of this study was to recognise the motivations to participate in triathlons among men and women respondents, and to evaluate the differences between them. The empirical research among triathletes (n = 1141) recognised the motives for participation in mass triathlon sporting events in accordance with four types of orientation: social, experience, factual, and result. Most important conclusions resulting from the conducted research indicate that women significantly more often displayed the will to feel unity and integration, as well as the desire to gain recognition in the eyes of others, as compared to men. For men, the desire to feel equal was significantly more important than for women. Both men and women indicated the desire to maintain good physical condition and health, which turned out to be a significant factor. For men, Group B—specifying the experience orientation, was deemed the most important, while for women the most important group of motives was Group D—specifying the result orientation.