This study examines the operational performance of a Manufacturing Execution System (MES)-based smart factory and presents a case study to provide practical insights for the effective adoption of smart factories by small- and medium-sized enterprises (SMEs) in Korea. While Industry 4.0 and Korea’s Manufacturing Innovation 3.0 policy have accelerated the digital transformation of manufacturing sites, the emerging paradigm of Industry 5.0 places greater emphasis on human-centricity, sustainability, and resilience. The case company, S Corporation, is a mid-sized automotive parts manufacturer that implemented an MES-based integrated platform encompassing production management, materials management through a Warehouse Management System (WMS), quality management via a Quality Management System (QMS), and equipment management. This integration enabled real-time monitoring and control of shop-floor operations, thereby enhancing data-driven decision-making. The case analysis, supported by a review of related literature, identifies significant quantitative improvements, including increased productivity, reduced defect rates, shorter lead times, and improved inventory turnover. In addition, several qualitative benefits were observed, such as enhanced process visibility, operational standardization, faster managerial decision-making, and a reduced workload for shop-floor operators. Overall, this study demonstrates a smart factory operational model that integrates the technological foundations of Industry 4.0 with the value-oriented principles of Industry 5.0. The findings provide meaningful implications for SMEs seeking to achieve sustainable and human-centered digital transformation in manufacturing.