Patients with Parkinson’s disease (PD) and essential tremor (ET) tend to lose weight progressively over years. Weight gain following deep brain stimulation (DBS) of the subthalamic nucleus (STN) for treatment of PD has been documented in several studies that were limited by small sample size and exclusive focus on PD patients with STN stimulation. The current study was undertaken to examine weight change in a large sample of movement disorder patients following DBS. A retrospective review was undertaken of 182 patient charts following DBS of the STN, ventralis intermedius nucleus of the thalamus (VIM), and globus pallidus internus (GPi). Weight was collected preoperatively and postoperatively up to 24 months following surgery. Data were adjusted for baseline weight and multivariate linear regression was performed with repeated measures to assess weight change. Statistically significant mean weight gain of 1.8 kg (2.8% increase from baseline, p = 0.0113) was observed at a rate of approximately 1 kg per year up to 24 months following surgery. This gain was not predicted by age, gender, diagnosis, or stimulation target in a multivariate model. Significant mean weight gain of 2.3 kg (p = 0.0124) or 4.2% was observed in our PD patients. Most patients with PD and ET gain weight following DBS, and this gain is not predicted by age, gender, diagnosis, or stimulation target.