The rapid advancement of information technology has encouraged businesses, particularly micro, small, and medium enterprises (MSMEs), to adopt integrated systems in order to improve business process efficiency. Putra Mandiri Building Materials Store, a retail business located in Depok, West Java, faced numerous operational challenges due to manual management practices, including stock data discrepancies, purchasing without official Purchase Orders, slow transaction recording, and the absence of real-time financial reporting. This study aims to analyze the implementation of an Odoo-based Enterprise Resource Planning (ERP) system to integrate the store's core business processes, namely purchasing, inventory management, and sales. A qualitative descriptive case study approach was employed alongside a design science methodology, encompassing problem identification, As-Is business process analysis, Odoo system configuration, To-Be business process analysis, and evaluation of benefits and limitations. The results demonstrate that Odoo's Purchase, Inventory, and Sales modules effectively automate stock updates, accelerate transaction document generation, and provide real-time operational information. The transformation from manual processes to an integrated system proved to enhance data accuracy and operational efficiency. Keywords – Enterprise Resource Planning; Odoo; MSME; Inventory Management; Business Process Integration.