Resource mobilization is a critical driver of effective development planning in Kenya’s devolved governance system. This study examines the influence of resource mobilization encompassing financial, human, and physical resources on the implementation of County Integrated Development Plans (CIDPs) in Nakuru County. Grounded in Resource-Based Theory, the study employed a correlational research design, targeting 258 stakeholders, including county officials, local administrators, and community representatives, with a sample of 78 respondents selected through purposive and stratified random sampling. Data were collected using structured questionnaires and analyzed through descriptive statistics (means, standard deviations, frequencies, percentages) and inferential statistics (Pearson’s correlation, multiple linear regression). Findings, presented in tables, revealed a strong positive correlation (r = 0.842, p < 0.01) and significant influence (β = 0.224, p < 0.05) of resource mobilization on CIDP implementation, assessed through project quality, conformity to objectives, and timeliness. The study concludes that effective resource mobilization enhances project efficiency and completion rates in Nakuru County’s CIDP implementation. Recommendations include developing robust resource allocation policies, fostering public-private partnerships, and enhancing stakeholder coordination to optimize resource use, offering actionable strategies for devolved governance in Kenya and similar contexts.