Achieving high-quality primary healthcare (PHC) remains essential to improving health systems performance and advancing progress towards attainment of universal health coverage, particularly in sub-Saharan Africa (SSA), where gaps in service delivery persist. Capacity-building interventions, such as mentorship, in-service training and supportive supervision, have been widely employed to improve the quality of PHC delivery. The evidence base is, however, fragmented across diverse settings, intervention types and outcome measures. This systematic review will examine the evidence on how capacity-building interventions improve the quality of PHC services in SSA, with a focus on the domains of effectiveness, safety, people-centredness, timeliness, equity, integration and efficiency as propounded by the WHO.

We will conduct a systematic review using established evidence synthesis methods and report the findings in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Eligible studies will include peer-reviewed and grey literature published in English between 2000 and 2025, focusing on capacity-building interventions aimed at improving PHC quality in SSA. We will search databases including PubMed, Embase, Web of Science, Scopus, Google Scholar and the African Journals Online. Study selection will follow the Population (PHC providers), Exposure (capacity-building interventions) and Outcome (quality of PHC delivery across WHO domains) framework. Quality assessment will use the Mixed Methods Appraisal Tool (MMAT). Data will be narratively synthesised using Atlas.ti software.

Ethical approval is not required because there will be no collection of primary data. Only published studies/records available on peer-reviewed literature and grey sources will be included. Findings will be disseminated through a peer-reviewed journal, academic conferences and stakeholder platforms in SSA.

The protocol has been registered in PROSPERO (CRD420251131534) and reported according to PRISMA-P guidelines.