Objective: The purpose of this study was to explore primary care sports medicine physicians' comfort, competence, education, and scope of training in caring for transgender and gender nonconforming (TGNC) patients/athletes. Design: Mixed-methods, cross-sectional survey. Setting: Online. Patients (or Participants): In total, 4300 e-mails were successfully sent with 252 eligible responses received from the American Medical Society for Sports Medicine members. Independent Variables: Previous relationships with TGNC persons; previous relationships with TGNC patients/athletes; frequency of care for TGNC patients/ athletes. Main Outcome Measures: The participants completed a 38-item tool used to assess perceived comfort and competence treating TGNC patients/athletes. Physicians defined "transgender" and described their thoughts on unfair competitive advantage of transgender athletes. Results: Most participants had worked with a TGNC patient (70.2%, n 5 177), but far fewer worked with a TGNC athlete (n 5 26.6%, n 5 67). Among the participants who provided a definition of transgender (n 5 183), only 28.4% (n 5 52) of participants were able to correctly define the term, whereas most were able to partially (57.9%, n 5 106) characterize the term. The most common mechanisms identified for learning about TGNC patients were reading peer-reviewed journal articles (44.8%, n 5 113) and CME (41.3%, n 5 104). Those with previous TGNC friend/family, patient, and athlete relationships had a significantly different level of comfort and competence treating TGNC patients/athletes. Conclusions: Previous care relationships with TGNC strongly influences comfort and perceived competence of primary care sports medicine physicians. Training, from unbiased peer-reviewed sources of data, is critical to improve care for TGNC patients/athletes.