Transgender and gender expansive (TGE) youth often seek a variety of gender-affirming healthcare services, including pubertal suppression and hormone therapy requiring that TGE youth and their parents participate in informed consent and decision making. While youth must demonstrate the ability to understand and appreciate treatment options, risks, benefits, and alternatives as well as make and express a treatment choice, standardized approaches to assess the capacity of TGE youth to consent or assent in clinical practice are not routinely used. This scoping (...) review identified the currently available data regarding adolescent capacity to consent to gender-affirming medical treatments. Articles relevant to assessing adolescent capacity for clinical decision-making were identified using OVID Medline, Web of Science, and PubMed. Articles were reviewed and thematically analyzed. Eight relevant articles were identified using three tools for measuring adolescent clinical decision-making capacity: Measure of Understanding, Measure of Competence, and MacArthur Competence Assessment Tool (MacCAT). These studies explored hypothetical treatment decisions, mental health treatment decisions, HIV treatment decisions, genetic testing decisions, and gender-affirming medical decisions. Only one study specifically examines the capacity of TGE youth to consent to medical treatments. Age was correlated with capacity in most, but not all studies. Other studies found cognitive measures (IQ, literacy, numeracy) may impact important aspects of capacity (understanding and reasoning). For clinicians caring for TGE youth, tools such as the MacArthur Competence Assessment Tool for Treatment (MacCAT-T) may prove useful, in conjunction with consideration of youth developmental abilities and utilization of shared decision-making practices. A standardized, collaborative approach to assessing TGE youth capacity would benefit TGE youth and their parents, and allow clinicians to more easily resolve ethical concerns. (shrink)