Latin American upper-middle-income countries (LAUMICs) face significant challenges in ensuring equitable access to sexual and reproductive health (SRH) for adolescents due to socioeconomic inequalities, migration, and historical violence. This systematic review examines the barriers and facilitators to sexual and reproductive health access for adolescent girls (≤19 years old) in vulnerable situations across Latin America. Using six databases, 391 articles were reviewed; 10 met the inclusion criteria, and 10 more were included through backward search, resulting in 20 analyzed studies. Structural barriers such as economic, regulatory, and institutional constraints were found to restrict SRH access, exacerbated by social stigma and negative narratives, especially in cases involving sexual violence and clandestine abortions. Facilitators included intersectoral collaboration, preventive education, and community networks, which improved access to and the quality of services for vulnerable populations. The findings emphasize the need for sustainable strategies that address structural inequalities and stigma while strengthening health systems, and intersectoral cooperation. Comprehensive, culturally tailored education and clear regulatory frameworks are essential to achieving equitable and sustainable SRH services. These insights offer practical guidance for public policy and program design in LAUMICs, particularly for addressing the needs of marginalized adolescent populations.