Abstract Background Access to comprehensive sexuality education (CSE) is crucial for adolescent health and well-being. Following UNESCO’s recommendations, Gabon revised its sex education policy in 2017 to better address adolescents’ sexual health needs. This study aims to map the capacities of the public health and education sector to implement Gabon’s CSE policy. Methods Semi-structured interviews were held with 15 professionals from ministries, NGOs, and development partners. Thematic analysis guided by Aluttis et al’s public health capacity model allowed to assess the existing capacities and gaps in leadership, organizational structures, partnerships, resources, and knowledge development for CSE. Results The implementation of CSE in Gabon is hindered by sociocultural and political factors, including the taboo on adolescent sexuality influencing perceptions of CSE content, natalist policies, and socio-economic disparities. Governmental involvement in CSE is limited to key ministries. Organizational structures for CSE lack cohesion due to changes in governance regimes and a lack of support for civil society organizations. Human resources are unevenly distributed, and financial constraints impede government initiatives, causing a strong reliance on external funding. An important role in supporting CSE is played by development partners and partnerships between stakeholders. While knowledge development for CSE is underway, monitoring and evaluation procedures are insufficient, and evidence mobilization by key professionals is insufficient. Conclusions Enhancing stakeholder collaboration, addressing structural constraints, and mobilizing human and financial resources are critical for effective CSE implementation in Gabon. Addressing these barriers requires coordinated efforts among stakeholders and addressing systemic challenges. This study provides insights for policymakers and practitioners to strengthen CSE programs and promote adolescent sexual health in Gabon. Key messages • CSE implementation is hindered by taboos on adolescent sexuality, natalist policies, and socio-economic gaps. • Evaluation and evidence mobilization deficits limit effectiveness.