The purpose of our research was twofold: to investigate the motivations for participating in a mass cycling event for amateurs and the motivational differences between men and women in cycling. This empirical study involving 385 cyclists was conducted during the fifth edition of the Skoda Bike Challenge held in Poznań in 2018. The event forms part of the UCI Gran Fondo World Series of events organized around the world, which are sanctioned by the Union Cycliste Internationale (UCI). A diagnostic survey method with a standardized interviewing technique was used to interview cyclists. The interview questionnaire was divided according to the MPAM-R scale (Motives for Physical Activity Measure–Revised). This scale assesses people’s motives for participating in physical activities. The following motivations were examined: appearance, fitness, social, competence/challenge, and enjoyment. Descriptive statistics were used. A chi-square test was used to determine characteristics between responses. Cramer’s φ for statistically significant scores was indicated. The research results show some differences between male and female motives for competitive amateur cycling. Statistically significant differences were found between the following motives: interest/enjoyment, competence/challenge, and fitness. This is important information from the point of view of promoting cycling and for organizers of cycling events in regions wishing to promote sports tourism as a form of sustainable development. An understanding of mass cycling motivations is needed, as such knowledge can be used to encourage cycling, which has a potentially positive effect on future cyclists’ physical and mental health. Learning about cycling motivations also allows us to determine which physical and mental health functions are fulfilled by mass sporting events and how to prepare for them. The motives for participating in mass cycling events for amateurs in Europe constitute an interesting field of research. The first part of the paper presents the literature review related to cycling in the context of motivations, sporting events, tourism, event management, and sustainable development, and the second part presents the results of our empirical study.