This paper aims to study the effects of internationalization as well as agency cost on operation performance of listed electronic companies in Taiwan. The findings show that companies with a higher degree of internationalization produced lower ROA and ROS However, further analysis on the moderate effect of agency cost on internationalization and operation performance tound companies with two characteristics resulted in lower ROA and ROS, while the degree of internationalization was higher:(1) companies whose board members' holdings were low: (2) companies with lower ratio of advertisement and R&D Discussion and suggestion for further research are provided. We hope that the finding will be valued for the manager.