A total of 15 individuals with cervical dystonia and good outcome after pallidal deep brain stimulation underwent resting‐state functional magnetic resonance imaging under three conditions: stimulation using a priori clinically determined optimal settings (ON‐Op), non‐optimal settings (ON‐NOp), and stimulation off (OFF). ON‐Op > OFF and ON‐Op > ON‐NOp were both associated with significant deactivation within sensorimotor cortex (changes not seen with ON‐NOp > OFF). Brain responses to stimulation were related to individual long‐term clinical improvement (R = 0.73, R² = 0.53, p = 0.001). The relationship was consistent when this model included four additional patients with generalized or truncal dystonia. These findings highlight the potential for immediate imaging‐based biomarkers of clinical efficacy. ANN NEUROL 2022;92:418–424