Purpose: Sexual and gender minority (SGM) people experience many health care disparities. We aimed to determine if medical students viewed sexual minority patients (lesbian, gay, or bisexual [LGB] men/women) as more complex than heterosexual patients, even when presenting with the same symptoms, and whether this perceived complexity affected confidence caring for LGB patients. Methods: A fictional patient with an upper respiratory infection was presented with systematic variation of the patient’s sexual orientation across six experimental conditions in an online, vignette-based experimental study. Participants rated their perception of the medical, therapeutic, and social complexity of the patient, and completed a measure of stigma toward SGM people. Finally, participants indicated their confidence caring for the presented patient. Results: Overall, 665 students participated. Participants viewed the LGB patients as more complex across all domains, relative to heterosexual patients. Perceived medical and social complexity predicted lower confidence caring for the patient. Participants reported lower confidence caring for gay male patients with indirect effects of medical and social complexity. LGB identity was broadly and indirectly associated with lower confidence through social complexity. Conclusion: Our results suggest students view LGB patients as more complex compared with heterosexual patients. Medical education programs must provide training about the effects of social biases on clinical judgments and care for LGB patients, as well as build skills to ensure confidence caring for LGB patients.