Importance: A dynamic elastomeric fabric orthosis could be a novel nonpharmacological treatment of motor symptoms among people with Parkinson's disease (PD)., Objective: To evaluate the efficacy of the orthosis in improving manual dexterity among people with PD., Design: A randomized trial with 60 participants (control group, n = 20; experimental group, n = 40). Manual dexterity was assessed in on-off states of the disease, with and without the orthosis., Setting: Burgos University Hospital (Burgos, Spain)., Participants: Consecutive nonprobabilistic sampling. Patients were included if they had been diagnosed with PD, had motor symptoms in at least one upper limb, and attended the hospital's neurology department. Participants were ages 48 to 89 yr, with an average disease duration of 5.38 yr (SD = 4.23). Exclusion criteria were tremor due to another neurological disease or a Montreal Cognitive Assessment score ≤26., Intervention: The experimental group used the orthosis on the most affected upper limb for 2 mo; the control group participants did not receive the orthosis., Outcomes and Measures: Manual dexterity was measured with the Purdue Pegboard Test, Minnesota Manual Dexterity Test, and Square Test. Paired t tests for related samples and analysis of covariance tests were used., Results: Some participants improved on some manual dexterity items while wearing the orthosis. However, it was not sustained when the orthosis was removed after 2 mo of use., Conclusions and Relevance: The orthosis may improve certain aspects of manual dexterity and functionality among people with PD, but only while it is worn. Plain-Language Summary: The common motor symptoms and declines in manual dexterity that people with Parkinson's disease (PD) experience can significantly affect their ability to perform activities of daily living as well as their quality of life. Manual dexterity is a strong predictor of the level of functional independence for people with PD. This study evaluated the efficacy of an elastomeric fabric orthosis to improve manual dexterity for people with PD. The study found that while wearing the orthosis the motor symptoms of PD were reduced and manual dexterity and upper limb functionality improved. Wearing the orthosis has the potential to enhance functionality, foster greater autonomy, and substantially improve the quality of life of people with PD., (Copyright © 2025 by the American Occupational Therapy Association, Inc.)