<p>Young adults in the United States experience a disproportionate burden of HIV and sexually transmitted infections (STIs), with Latino populations and residents of California’s inland regions facing compounded disparities. This study examined multilevel barriers to HIV and STI testing among Latino college students in the California Inland Empire using Group Concept Mapping (GCM), a mixed-methods participatory approach. Twenty-six students participated in brainstorming sessions, and nineteen completed sorting and rating activities. Analyses identified five clusters of barriers: access, awareness, and competing priorities; knowledge, social norms, and normalization of testing; structural and healthcare system barriers; emotional and relational barriers; and moralized sexual health stigma rooted in family, cultural, and religious norms. All clusters were rated as moderately to highly important, with access- and knowledge-related barriers emerging as the most influential. Go-zone analyses highlighted actionable targets, including improving access to low-cost testing, integrating sexual health into routine care, enhancing privacy and confidentiality, and fostering supportive provider and peer environments. Barriers perceived as less acceptable to address included culturally embedded stigma and limited sexual health education. Findings underscore the need for multilevel, culturally grounded interventions that address structural, interpersonal, and sociocultural factors to improve testing engagement and advance sexual health equity among Latino college students in underserved regions.</p>