BackgroundSignificant health disparities between sexual minority individuals (that is, lesbian, gay, bisexual, or transgender [LGBT]) and heterosexual individuals have been demonstrated.AimTo understand the barriers and facilitators to sexual orientation (SO) disclosure experienced by LGBT adults in healthcare settings.Design and settingMixed methods systematic review, including qualitative, quantitative, and mixed methods papers following PRISMA guidelines.MethodStudy quality was assessed using the Mixed Methods Appraisal Tool (MMAT) and a qualitative synthesis was performed. Studies were included if their participants were aged ≥18 years who either identified as LGBT, had a same-sex sexual relationship, or were attracted to a member of the same sex.ResultsThe review included 31 studies representing 2442 participants. Four overarching themes were identified as barriers or facilitators to SO disclosure: the moment of disclosure, the expected outcome of disclosure, the healthcare professional, and the environment or setting of disclosure. The most prominent themes were the perceived relevance of SO to care, the communication skills and language used by healthcare professionals, and the fear of poor treatment or reaction to disclosure.ConclusionThe facilitators and barriers to SO disclosure by LGBT individuals are widespread but most were modifiable and could therefore be targeted to improve healthcare professionals’ awareness of their patients’ SO. Healthcare professionals should be aware of the broad range of factors that influence SO disclosure and the potential disadvantageous effects of non-disclosure on care. The environment in which patients are seen should be welcoming of different SOs as well as ensuring that healthcare professionals’ communication skills, both verbal and non-verbal, are accepting and inclusive.