This study aimed at establishing the effect of inventory management practices on the operational performance of Mombasa County government. The specific objectives included the following: to examine the impact of JIT model on the operational performance of Mombasa County government; to assess the effect of Activity Based Costing (ABC) on the operational performance of Mombasa County government; to determine the impact of Economic Order Quantity (EOQ) on the operational performance of Mombasa County government and to establish the impact of stock taking practice on the operational performance of Mombasa County government. The research study reviewed Just in Time Theory, Systems theory and the transactional theory. This study used a descriptive survey design. The target population was all the 250 employees working in Mombasa County government that included ICT officers, Finance officers, Budgeting officers, Internal Audit officers and Procurement officers. Sample size of 96 employees was drawn from and was selected by the use of stratified random sampling. Data was collected using a questionnaire. Data analysis was done with the aid of SPSS version 28. Inferential statistics was displayed by the use of correlations and regression analysis. The ethical considerations for this study included confidentiality, informed consent, privacy and anonymity. Correlation analysis revealed that there was a significant correlation between the Operational Performance of the County Government of Mombasa and Activity Based Costing practice (β = 0.321, p˂ 0.05). This is followed by Economic Order Quantity X3 (β = 0.289, p˂ 0.05), Stocktaking X4 (β = 0.251, p˂ 0.05), and Just in Time Model X1 (β = 0.243, p˂ 0.05), in that order.