BACKGROUND: Caring for adolescents living with HIV/AIDS (ALHIV) can be overwhelming due to their unique needs. Ghana is currently among nine countries in West and Central Africa contributing to 90% of new paediatric infections in the sub-region with a growing population of ALHIV. Regardless, gaps in paediatric related care including healthcare providers (HCPs) capacity issues have been identified. This study sought to assess the competencies of adolescent-oriented healthcare providers before, and after interventionist training to inform recommendation that would guide the psychosocial care they give to ALHIV. METHODS: The study adopted a mixed methods approach with a non-randomized interventional study involving three-phase multi-methods. The sample consisted of 28 adolescent-oriented and multi-disciplinary healthcare providers at the Cape Coast Teaching Hospital (CCTH) in Ghana. Data were obtained in three phases, namely, a baseline survey, interventionist training, and post-training in-depth interviews. Quantitative data were analyzed using Stata version 13 for descriptive analysis while the qualitative data were analyzed thematically using NVivo version 11. RESULTS: Although the majority of the HCPs claim to be knowledgeable about adolescent health issues (n = 21, 75.0%), only about a third (n = 10, 35.7%) could correctly define who an adolescent is. The majority (n = 18, 64.3%) had not received any training on how to work with the adolescent client. The main areas identified for improvement in the ALHIV care in phase 1 included issues with psychosocial assessment, communication and treatment adherence strategies, creating an adolescent-friendly work environment, and availability of job aids/protocols. During the post-training interviews, participants reported an improved understanding of the characteristics of an adolescent-friendly site and basic principles for ALHIV care. They were also able to correctly describe the widely used adolescent health assessment tool; the HEEADSSS. Post intervention interviews also revealed HCPs perception on increased practice related confidence levels and readiness to implement new knowledge and skills gained. CONCLUSION: This study has shown that targeted training on routine ALHIV care is effective in increasing HCPs knowledge, skills and confidence. Addressing the healthcare system/facility related gaps serves as an impetus for improved ALHIV care among HCPs.