Objective To determine the immediate effect of a portable, myoelectric elbow-wrist-hand orthosis on paretic upper extremity (UE) impairment in chronic, stable, moderately impaired stroke survivors. Design Observational cohort study. Setting Outpatient rehabilitation clinic. Participants Participants exhibiting chronic, moderate, stable, poststroke, UE hemiparesis (N=18). Interventions Subjects were administered a battery of measures testing UE impairment and function. They then donned a fabricated myoelectric elbow-wrist-hand orthosis and were again tested on the same battery of measures while wearing the device. Main Outcome Measures The primary outcome measure was the UE Section of the Fugl-Meyer Scale. Subjects were also administered a battery of functional tasks and the Box and Block (BB) test. Results Subjects exhibited significantly reduced UE impairment while wearing the myoelectric elbow-wrist-hand orthosis (FM: t 17=8.56, P<.0001) and increased quality in performing all functional tasks while wearing the myoelectric elbow-wrist-hand orthosis, with 3 subtasks showing significant increases (feeding [grasp]: z=2.251, P=.024; feeding [elbow]: z=2.966, P=.003; drinking [grasp]: z=3.187, P=.001). Additionally, subjects showed significant decreases in time taken to grasp a cup (z=1.286, P=.016) and increased gross manual dexterity while wearing a myoelectric elbow-wrist-hand orthosis (BB test: z=3.42, P<.001). Conclusions Results suggest that UE impairment, as measured by the Fugl-Meyer Scale, is significantly reduced when donning a myoelectric elbow-wrist-hand orthosis, and these changes exceeded the Fugl-Meyer Scale's clinically important difference threshold. Further, utilization of a myoelectric elbow-wrist-hand orthosis significantly increased gross manual dexterity and performance of certain functional tasks. Future work will integrate education sessions to increase subjects' ability to perform multijoint functional movements and attain consistent functional changes.