Reliability and quality of electricity are important for industrial operations. A reliable power generation system and well-organized management pay special attention to these two aspects. The company implements a quality management system, ISO 9001:2015 to maintain consistency and improve power plant performance. In addition, the implementation of corporate culture is expected to improve organizational performance. The purpose of this study is to examine the effect of ISO implementation and corporate culture on power plant performance. Sampling in this study uses non-probability sampling with purposive sampling technique. Data were collected from 232 employee respondents and analyzed using Structural Equation Modeling (SEM) -AMOS program. The results show that ISO implementation has a positive effect on power plant performance and corporate culture is a mediating variable that can improve power plant performance. The implication is that the policy of prioritizing the availability of power plants, the process approach in implementing the quality management system, and trustworthiness in implementing culture are the right choices in improving power plant performance.