The REBAHS LPSP II action launched in May 2022 by International Medical Corps (IMC) and Première Urgence Internationale (PUI) in Lebanon is a continuation of previous initiatives implemented in Primary Healthcare Centers (PHCCs) with the key aim to support service provision in PHCCs. This study aims to present a multi-faceted impact evaluation approach, quantifying the outcomes of the action and identifying areas for improvement. A mixed-method approach was adopted, including quantitative and qualitative tools to assess the impact of the initiative's health sector. Indicators of PHCC service utilization were extracted from the National Health Information System (PHENICS) and analyzed through descriptive analysis, interrupted time series analysis, and cost-effectiveness analysis. Key-informant interviews (KII) were conducted with donors and stakeholders, and Focus Group Discussions (FGDs) were implemented with PHCC staff members to gain a deeper understanding of the impact, challenges, and areas for improvement of the initiative. The action resulted in an overall increase in the proportion of children being screened for malnutrition, women being screened for breast cancer via mammogram testing, and a high number of antenatal care visits. Improved access to care, patient satisfaction, quality of care, and disease detection and management among other positive impacts have been highlighted. Barriers to implementation including administrative burdens, staff turnover, and financial constraints among others have been suggested. Lessons learned and recommendations for future program design have been highlighted. This study may serve as a model for enhancing healthcare systems globally by enhancing global funding models, optimizing resource allocation, and improving program impact, specifically in conflict-affected settings and countries with limited resources, thereby enhancing healthcare access, health service delivery, and program sustainability.