This study was designed to examine a 3-week modified constraint-induced movement therapy (CIMT) to the less-affected arm of patients with Parkinson's disease (PD) would improve function of the more-affected arm in PD. The subjects were 6 institutional older adults with PD and clients of the social welfare facilities. The subjects (2 men, 4 women) ranged in age from 66 to 90 years (mean age 77.2 yrs). Three clinical tests were used to determine the improvement of functional activity between before and after modified CIMT. The tests included Unified Parkinson's Disease Rating Scale (UPDRS). Wolf Motor Function Test (WMFT), and Action Research Arm Test (ARAT). There were significantly differences after the modified CIMT for time performance in WMFT and pinch in ARAT (p<.05), No significant difference was noted after the modified CIMT for UPDRS and functional ability scale in WMFT. Therefore, the modified CIMT might improve time performance and is available to therapeutic program helping them improve functional ability for upper extremity in Parkinson's disease.