We compared radiological and clinical outcomes between multilevel lateral lumbar interbody fusion (LLIF) + hybrid posterior fixation (PF) and multilevel LLIF + conventional open PF in patients with adult spinal deformity (ASD). Patients who underwent minimally invasive surgery for ASD in a single institution between 2014 and 2018 were retrospectively reviewed. Fifty-six patients (hybrid PF, 30; open PF, 26) who underwent ASD correction surgery were enrolled between 2014 and 2018. We evaluated patients’ demographics, clinical outcomes, and radiographical parameters in each group. There was significantly less estimated blood loss in the hybrid PF group (662.8 mL vs. 1088.8 mL; p = 0.012). The CRP level 7 days after surgery was significantly lower in the hybrid PF group (2.9 mg/dL vs. 4.3 mg/dL; p = 0.035). There was no significant difference between the two groups in other demographic variables, visual analog scores for back pain and leg pain, Oswestry Disability Index, coronal Cobb angle, lumbar lordosis, pelvic tilt, pelvic incidence-lumbar lordosis mismatch, and sagittal vertical axis. There was a significantly higher percentage of major complications in the open PF group (42.3% vs. 13.3%; p = 0.039). Thus, LLIF + hybrid PF for ASD corrective surgery may be comparable to LLIF + open PF in terms of clinical and radiographic outcomes.