Abstract: Monitoring and evaluation (M&E) systems play a pivotal role in ensuring the success of global projects undertaken by private and non-governmental organizations. The utilization of M&E systems is vital for project accomplishment and the adherence to predefined scopes. Nevertheless, organizations frequently encounter challenges in this regard, as exemplified by the case of Plan International Kenya. This organization faced issues related to stakeholder engagement and project implementation costs due to initial shortcomings in their M&E systems. This study aims to address the existing research gaps, particularly concerning key variables such as competency levels within M&E systems, stakeholder participation, and the costs associated with monitoring and evaluation. This research delves into the intricate relationships between monitoring resources, the competence levels associated with M&E systems, stakeholder involvement, and the overall performance of Plan International health projects in Nairobi County. The theoretical underpinnings of this study draw upon the Theory of Change, the Resource-Based View Theory, and the Results Theory. The research methodology incorporated a purposive sampling approach, targeting a population of 45 staff members actively engaged in Plan International health projects within Nairobi County. Data collection methods included both questionnaires and interviews, each subjected to rigorous reliability assessments. Quantitative data were analyzed using SPSS software version 24, with results being presented through descriptive statistical methods. Qualitative data was thematically analyzed, aligning with the study defined objectives and thematic areas.