Objective: The primary aim of this study was to determine the prevalence and one-season incidence of symptoms of common mental disorders (CMD; distress, anxiety/depression, sleep disturbance, eating disorders, adverse alcohol use) among European professional football referees. A secondary aim was to explore the view of European professional football referees on consequences, support and needs related to these symptoms. Methods: An observational prospective cohort study with three measurements over a follow-up period of one season (2015-2016) was conducted among central or assistant professional football referees from Belgium, Finland, France, Germany, Norway, Russia, Scotland and Sweden. Using validated questionnaires to assess symptoms of CMD (self-reported and not clinically diagnosed), an electronic questionnaire in English and French was set up and distributed by the eight football federations involved. Results: A total of 391 referees (mean age of 33years old; mean career duration of 7 years) were enrolled, of which 292 completed the follow-up period. Baseline 4-week prevalence rates were 6% for distress, 12% for anxiety/depression, 9% for sleep disturbance, 19% for eating disorders and 17% for adverse alcohol use. The one-season incidence of symptoms of CMD was 10% for distress, 16% for anxiety/depression, 14% for sleep disturbance, 29% for eating disorders and 8% for adverse alcohol use. Conclusion: While symptoms of CMD occur among professional football referees and can influence negatively refereeing performances, the development of specific support measures for referees are needed in order to manage properly these symptoms of CMD.