This paper examined the effect of working capital management practices on the operational performance of selected supermarkets with the national network in Kenya focusing on inventory and creditors’ management as well as receivables and liquidity practices. The paper was pegged on Agency Theory, Iceberg Theory of Money Management and Cash Management Theory. Guided by descriptive research design, 52 branch managers were sampled from four major supermarkets using both the stratified and random sampling methods. Data were analyzed using both descriptive and inferential statistical analysis. Findings revealed that inventory and creditors management practices had a very low effect on the operational performance of supermarkets in Kenya. The study, therefore, recommends that supermarkets should introduce a system where managers are fully equipped with working capital management skills. This should be done continuously to prevent the occurrence of severe liquidity challenges which have witnessed in the past.