STUDY DESIGN: Prospective study. OBJECTIVE: Our objectives were to evaluate the prevalence of sagittal spinopelvic malalignment in a consecutive series of patients with Parkinson disease (PD) and to identify factors associated with sagittal spinopelvic deformity in this population. SUMMARY OF BACKGROUND DATA: PD is a degenerative neurological condition characterized by tremor, rigidity, bradykinesia, and loss of postural reflexes. The prevalence of spinal deformity in PD is higher than that of age-matched adults without PD. METHODS: This study was a prospective assessment of consecutive patients with PD presenting to a neurology clinic during 12 months. Inclusion criteria included age more than 21 years and diagnosis of PD. Age- and sex-matched control group was selected from patients with cervical spondylosis. Clinical and demographic factors were collected including Unified Parkinson Disease Rating Scale score and Hoehn and Yahr stage. Full-length standing spine radiographs were assessed. Patients were grouped into either low C7 sagittal vertical axis (SVA) (<5 cm) or high C7 SVA (≥5 cm) and into matched (≤10°) or mismatched (>10°) pelvic incidence (PI)-lumbar lordosis. RESULTS: Eighty-nine patients met criteria (41 males/48 females), including 52 with low C7 SVA and 37 with high C7 SVA. Significantly higher prevalence of high C7 SVA was found in PD (41.6 vs. 16.8%; P < 0.001). The high C7 SVA group was significantly older (72.4 vs. 65.1 yr; P < 0.001) and had a higher proportion of females (68% vs. 44%; P = 0.034), greater severity of PD based on Hoehn and Yahr stage (1.89 vs. 1.37; P < 0.001) and Unified Parkinson Disease Rating Scale (30.5 vs. 17.2; P = 0.002. Unified Parkinson Disease Rating Scale significantly correlated with C7 SVA (r = 0.474). Compared with the matched (≤10°) PI-lumbar lordosis group, the mismatch PI-lumbar lordosis group had higher C7 SVA, higher PI, higher pelvic tilt, lower lumbar lordosis, and lower thoracic kyphosis (P ≤ 0.003). CONCLUSION: Patients with PD have a high prevalence of sagittal spinopelvic malalignment than control group patients. Greater severity of PD is associated with sagittal spinopelvic malalignment. LEVEL OF EVIDENCE: 3.