AIM:To describe the acceptability and the perceptions of athletes and staff members (ie, end-users) towards an online sports-health surveillance system. METHODS:A pilot study with a mixed-methods approach was pursued. Descriptive analysis was conducted to present the adherence of judo (n=34), swimming (n=21) and volleyball (n=14) athletes to an online registration of their sport exposure and any health complaints between April 2014 and January 2015. End-users' perceptions towards the system were investigated qualitatively with semistructured interviews (n=21). Qualitative analysis was based on the constant comparative method using principles of the grounded theory. RESULTS:The response rates of judo, swimming and volleyball athletes were 50% (SD 23), 61% (SD 27) and 56% (SD 25), respectively. Most athletes found it simple to register their sport exposure and health complaints online; however, personal communication was still preferred for this purpose. The system facilitated the communication between medical and trainer staff, who were able to identify in the system reports health complaints from athletes that were not necessarily communicated face-to-face. Therefore, staff members reported that they were able to intervene earlier to prevent minor health complaints from becoming severe health problems. However, staff members expected higher adherence of athletes to the online follow-ups, and athletes expected to receive feedback on their inputs to the system. CONCLUSION:An online system can be used in sporting settings complementary to regular strategies for monitoring athletes' health. However, providing feedback on athletes' inputs is important to maintain their adherence to such an online system.