Objective This study was undertaken to identify preoperative predictive factors of long‐term motor outcome in a large cohort of consecutive Parkinson disease (PD) patients with bilateral subthalamic nucleus deep brain stimulation (STN‐DBS). Methods All consecutive PD patients who underwent bilateral STN‐DBS at the Grenoble University Hospital (France) from 1993 to 2015 were evaluated before surgery, at 1 year (short‐term), and in the long term after surgery. All available demographic variables, neuroimaging data, and clinical characteristics were collected. Preoperative predictors of long‐term motor outcome were investigated by performing survival and univariate/multivariate Cox regression analyses. Loss of motor benefit from stimulation in the long term was defined as a reduction of less than 25% in the Movement Disorder Society–sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS‐UPDRS) part III scores compared to the baseline off‐medication scores. As a secondary objective, potential predictors of short‐term motor outcome after STN‐DBS were assessed by performing univariate and multivariate linear regression analyses. Results In the long‐term analyses (mean follow‐up = 8.4 ± 6.26 years, median = 10 years, range = 1–17 years), 138 patients were included. Preoperative higher frontal score and off‐medication MDS‐UPDRS part III scores predicted a better long‐term motor response to stimulation, whereas the presence of vascular changes on neuroimaging predicted a worse motor outcome. In 357 patients with available 1‐year follow‐up, preoperative levodopa response, tremor dominant phenotype, baseline frontal score, and off‐medication MDS‐UPDRS part III scores predicted the short‐term motor outcome. Interpretation Frontal lobe dysfunction, disease severity in the off‐medication condition, and the presence of vascular changes on neuroimaging represent the main preoperative clinical predictors of long‐term motor STN‐DBS effects. ANN NEUROL 2021;89:587–597