This study aims to analyze the application of Knowledge Management with the Plan, Do, Check, Act (PDCA) method as a competitive advantage in PT. Mutuagung Lestari, TBK. The research method used in this study is a qualitative approach by utilizing the Nvivo 14.0 application to analyze interview data related to the implementation of Knowledge Managemet and the PDCA method is used to evaluate the cycle of Knowledge Managemet implementation starting from planning, implementation, supervision, to continuous improvement of PT. Mutuagung Lestari, TBK. The results of the study show that the application of Knowledge Management at PT. Mutuagung Lestari has covered aspects of knowledge acquisition, knowledge sharing, knowledge utilization, and Knowledge Management Approaches, with significant results in supporting innovation, efficiency, and business sustainability. Despite the challenges in knowledge sharing, data management, and a culture of collaboration, the company has demonstrated commitment through human resource development and the improvement of supporting infrastructure. Analysis with NVivo revealed that the Plan and Do stages in the PDCA method have gone well through training and discussion forums, while the Check and Act stages require improvement in evaluation and continuous improvement. Knowledge Management is also a key element in decision-making and process efficiency, while supporting companies to rely on a competent workforce as a key competitive advantage. With a commitment to professional service and client satisfaction, the reputation of PT. Mutuagung Lestari is getting stronger in the certification sector.