Purpose: The purpose of this study was to investigate the effects of passive upper arm exercise on range of motion, muscle strength, and muscle spasticity in hemiplegic patients with cerebral vascular disease. Methods: A quasi-experimental design with nonequivalent control group was utilized. According to inclusion criteria, 25 patients were assigned to the control group with routine care, followed by 25 to the intervention group with passive exercise for 30 minutes per session, twice a day for 2 weeks. Eighteen patients in the intervention group and 17 in the control group completed the posttest measurement, including range of motion for upper arm joints, manual muscle test, and Modified Ashworth Scale for muscle spasticity. Results: The intervention group had a significantly improved range of motion in the shoulder and wrist joints. No interaction effect was found for the elbow joint. No significant differences were found in muscle strength or muscle spasticity between the groups. Conclusion: Results of the study indicate that passive exercise safely applied for two weeks improves range of motion in joints of the upper arm in these patients. Further study with long-term follow-up is needed to verify the role of passive exercise in preventing muscle spasticity in this population.