The purpose of this study is to analyse the implementation level of quality management system ISO 9001 in Electricity Sector Company in Indonesia, including the barriers during the implementation. Quantitative analysis is performed to determine the implementation level of ISO 9001 based on the seven quality management principles. The data in this descriptive study were obtained through a survey. A number of 84, out of 105 samples of PT ABC business units that are engaged in electricity generation, transmission, distribution, or supporting units in Indonesia participated in the survey. The questionnaire in the survey is developed based on previous studies and the quality management system standard. The results show that process approach, customer focus, evidence-based decision making, relationship management, leadership principle, and improvement have near to good implementation level, while engagement of people have a slightly good implementation level. The results also indicate that there are five main barriers in which were experienced during the implementation of ISO 9001, consisting of two behavioural and cultural barriers, two technical barriers, and one organizational barrier.