[Purpose] The aim of this study was to determine the effects of mental practice on muscle activity of the upper extremity and performance of daily activities in chronic stroke patients. [Subjects and Methods] In this research, mental practice was conducted by 2 chronic hemiplegic stroke patients. Mental practice was conducted 30 minutes a day, 5 times a week, for 2 weeks. Evaluation was conducted 4 times before and after intervention. Muscle activity was measured using a surface electromyogram test, and the Modified Barthel Index was used to measure changes in the ability to carry out daily activities. [Results] Both the muscle activity of the upper extremity and capability to perform daily activities showed improved outcomes after mental practice was conducted. [Conclusion] Through this research, mental practice was proven to be effective in improving the muscle activity of upper extremity and capability to perform daily activities in chronic hemiplegic stroke patients.