This study conducted an empirical analysis using a structural equation model to examine the relationships among quality management systems, absorptive capacity, and business performance, with the aim of investigating the impact of quality management systems and absorptive capacity on the competitiveness of small and medium-sized manufacturing firms and exploring ways to enhance business performance. Direct and indirect effects were analyzed through path analysis and other methods. The quality management system was defined by the ISO 9001 requirements: implementation of management responsibility, execution of resource management, establishment of product realization processes, and operation of measurement, analysis, and improvement. Absorptive capacity was defined as efficient quality management innovation and advanced production technology innovation. Business performance was composed of operational performance, customer performance, and financial performance. The research findings can be summarized as follows. First, the construction and operation of quality management systems were found to have a positive impact on absorptive capacity, namely efficient quality management innovation and advanced production technology innovation. Second, the core elements of absorptive capacity were found to individually have positive effects on business performance measures including financial performance, customer performance, and operational performance. Third, operational performance contributed to customer performance, and customer performance contributed to financial performance. Fourth, a mediating effect was confirmed whereby the construction and operation of quality management systems indirectly affected customer performance through the pursuit of absorptive capacity, specifically efficient quality management innovation and advanced production technology innovation. The implications of this study are as follows. First, small and medium-sized manufacturing firms need efficient quality management innovation and advanced production technology innovation as absorptive capacities suitable for manufacturing firms to enhance competitiveness. Second, the stable construction and securing of quality management systems is necessary for the effective pursuit of absorptive capacity. Third, a foundation for corporate growth can be established that improves financial performance in the long term through the enhancement of operational performance and customer performance. Furthermore, this study proposed appropriate absorptive capacity for enhancing the competitiveness of small and medium-sized manufacturing firms, operational strategies for absorptive capacity by type of business performance, and the strengthening of quality management system operations for the effective pursuit of absorptive capacity. Additionally, it proposed expanding the evaluation weight of non-financial performance measures—operational performance and customer performance—that reflect a firm's growth potential, moving beyond the classical assessment of financial performance alone.