<p>Participation in cancer clinical trials is essential for advancing medical knowledge, improving patient outcomes, and ensuring equitable access to emerging therapies. However, oncology clinical trial participants do not reflect the population affected by cancer. In particular, racial and ethnic minorities, rural residents, and individuals from lower socioeconomic backgrounds continue to be significantly underrepresented in oncology clinical trials overall, and among trials evaluating patients with head and neck cancer (HNC), relative to their frequency in the general population. This review applies the social ecological model to identify and categorize barriers to equitable clinical trial accrual across individual, interpersonal, institutional, community, and policy levels. Addressing these multilevel barriers requires the concerted efforts of researchers, clinicians, community leaders, and policymakers. Commitment to inclusive trial design and implementation is essential to ensuring that the benefits of cancer research are equitably distributed. Clinical research must reflect the populations it seeks to serve, so that all patients, not just a select few, benefit from the future of oncology innovation.</p>