Introduction: Men who have sex with men (MSM) are at greater risk of certain infectious diseases. Prevention, screening, and even treatment of these conditions can be provided by a primary care physician (PCP); this requires that patients have disclosed their sexual orientation to their doctor. We sought to explore the extent to which MSM disclosed their sexual orientation to their doctor and whether this affected care and the doctor-patient relationship. Materials and Methods: The HomoGen study, conducted from May 2016 to March 2017, was based on an online questionnaire targeting the MSM population and exploring the disclosure of sexual orientation to the GP and any barriers to doing so, as well as the screening and prevention of sexually transmitted infections (STIs) that had been performed. Results: Among the 1,879 participants, 87.3% had a primary care physician and 58.0% had disclosed their sexual orientation to them. Participants who had disclosed their sexual orientation were, on average, older, as were those who had initiated the disclosure and those who considered it important. Participants who disclosed their sexual orientation to their primary care physician were screened for STIs by their physician more frequently, and the physician more frequently offered them hepatitis A vaccination. After disclosing their sexual orientation, 84.4% of participants considered their relationship with the physician unchanged. Conclusion: The majority of MSM have a primary care physician, who is aware of their sexual orientation in most cases. This information is associated with better medical care. Physicians need better training to encourage the disclosure of sexual orientation for a more effective approach to their patients’ sexual health, particularly among MSM.