<i>Aim</i>: This study aims to provide a comprehensive overview of the Annual Operational Planning (AOP) process, a key health sector planning and harmonization approach, in Kebbi State, Nigeria, from 2020 to 2024, focusing on nine optimal planning parameters: state ownership, stakeholder participation, sector harmonization, evidence-based, timeliness, executive sign-off, quarterly tracking, dissemination, and sustainability. <i>Methods</i>: Review of AOP program reports, state-relevant reports, and stakeholders’ interviews. Employing a mixed-methods research design, the study integrates quantitative data derived from secondary sources like annual reports and policy documents with qualitative data from semi-structured interviews with key stakeholders. Descriptive statistics and time-series analysis are used for quantitative data to study progress and trends in each milestone, while thematic analysis of interview transcripts helps to elucidate factors influencing implementation and outcomes. <i>Results:</i> Findings highlight a progressive improvement in the annual operational planning across several of the planning parameters over the years from the baseline in 2020, including in participatory engagement of the lower levels of the health sector (bottom-up approach), using evidence to inform planning; timely development of the AOP to inform health budget; and regular tracking of the plan. However, challenges persist in the government funding of stakeholders’ engagement, particularly the bottom-up approach at the Local Government Health Authorities (LGAs) level, which may affect the inclusiveness of the process in the future. <i>Conclusion</i>: The study concludes that the annual operational planning in Kebbi State has seen notable improvement across multiple planning parameters, assuring the effectiveness and sustainability of the process as a key planning tool. However, allocating adequate resources, including budget and human resources, to facilitate a participatory approach in the AOP development process is critical for continuous success. This study contributes to the broader discourse on health sector planning in developing contexts, offering valuable insights for policymakers, health managers, and stakeholders in designing and implementing effective and harmonized health plans.
