The purpose of this research is to evaluate the effectiveness of implementation Quality Management System (ISO 9001: 2000) in gas processing plants of National Iranian Gas Company using balanced scorecard approach. More specifically, we chose the balanced scorecard framework to examine five well-known gas processing plants in National Iranian Gas Company from four different perspectives in order to provide a more comprehensive view of organizational performance after the registration of ISO 9001. The methodology used in this research comprised administering a questionnaire to 360 respondents in the company in order to find out the results of using ISO 9001: 2000 on the firms under study based on four BSC aspects and. The results indicated that: First, the BSC could be used successfully to measure the performance of quality systems in the gas processing plants of NIGC. Second, the findings indicated ranking of five plants based on the BSC perspective. However, the customer and learning perspectives are neglected in the target companies.