Purpose: In this article, the authors report a case of acquired stuttering associated with Parkinson's disease (PD) that was responsive to unilateral subthalamic nucleus deep-brain stimulation (STN DBS) in the language-dominant hemisphere. Method: A single-subject, masked, multiple baseline design was used to evaluate the effects of unilateral left STN DBS on stuttering associated with PD. The patient underwent 3 formal speech assessments of spontaneous speech and the reading of passages with DBS off and on. Speech samples were videotaped and placed in random order, and 2 independent speech-language pathologists calculated the percentage of stuttered syllables and classified individual stuttering events. Results: Stuttering improved significantly in the DBS-on condition. In total, 10% of syllables were affected by stuttering events with DBS off, and less than 1% of syllables were affected by stuttering events with DBS on (n = 2,281 syllables, p < .00001, in a χ2 test). The effect of unilateral STN DBS on stuttering was relatively independent of whether the patient was on or off dopaminergic medications. Conclusion: This article emphasizes the important role of the subthalamic region in the motor control of speech and language. © American Speech-Language-Hearing Association.