Upper extremity motor function impairment is the common symptom in chronic stroke patients and result in reducing the usage of the affected arm in daily living. Recent research suggest that stroke patients may benefit from mirror therapy in upper extremity motor functions. The purpose of this study was to evaluate the effects of mirror therapy on upper extremity motor function in patients of chronic stroke patients. 16 chronic stroke (onset ＞ 6 months) patient were included in this study and randomly assigned to the mirror therapy (MT) group (n = 8) and the control (RC) group (n = 8). The mirror therapy group received mirror therapy program for 1 hour and conventional therapy for 0.5 hour per day, 5 days a week, in 4 weeks. The control group received the doesmatched conventional therapy. The Fugl-Meyer Assessment (FMA) and Micro-mini Motion-logger, were used to assess the changes in upper extremity motor function and the ratio of affected arm use to non-affected arm use after intervention. The visual analog scales were also applied for assessing the level of pain and fatigue that may be induced by intervention. In the upper extremity function, the scores of FMA increased more in MT group (6.5 ± 4.3, Mean ± SD) than in RC (3.12 ± 2.03) group (p ＜ .05). The ratio of affected arm use to non-affected arm use reduced more in MT (-0.24 ± 0.16) group than in RC (0.06 ± 0.16) group significantly (p ＜ .05). No significant difference was found in pain and fatigue level between two groups. This study supports that both therapies are effective for upper extremity motor function rehabilitation in chronic stroke patients. Therefore, chronic stroke patients made more improvement in upper motor functions with combined mirror therapy with conventional therapy. However, it would be noticed that the ratio of affected arm use to nonaffected arm use may be reduced after mirror therapy intervention.