Introduction: Misgendering of transgender/gender nonconforming (TGNC) individuals in healthcare settings can lead to worse mental and physical health outcomes, as well as decreased utilization of care, compromising the patient’s overall safety and well-being. While the negative impacts of misgendering are well documented, few studies have investigated the factors that contribute to this phenomenon. This study aimed to identify factors that contribute to the misgendering of TGNC individuals in the healthcare setting. We also identify solutions that future research and system engineering approaches can explore. Methods: Twenty in-person and Zoom interviews with transgender patients, gender affirming providers, and transgender individuals who had experience both as providers and patients, across the UCSD healthcare system, were conducted. Interviews were conducted one-on-one using an open-ended topical guide and recorded. Audio files were de-identified and transcribed verbatim. Qualitative analysis was performed by two independent study personnel who hand coded the transcripts using Constructivist Grounded Theory qualitative methods. Results: Analysis revealed several preliminary misgendering themes and subthemes that describe various sources, risk factors, modifying factors, as well as implications of misgendering on patient engagement with healthcare (Table 1). Preliminary solution themes included developing systems to provide continual training and feedback to patient-facing staff, provider self-practice, inclusive naming, and resolving issues with the EHR. Additionally, a four-step provider response to misgendering a patient was recommended with the following steps: 1) acknowledge 2) apologize 3) move on 4) take actions to prevent recurrence. Conclusions: Our data suggest that misgendering is ubiquitous and perpetuated by numerous sources operating at multiple levels within the healthcare system. Any potential solution to reduce this harmful phenomenon will require a multifaceted approach targeting behavioral, technological, and implementation domains. Future research should employ human factors, improvement science, risk management, and biopsychosociotechnical systems approaches. SOURCE OF Funding: None.