This comparative cohort study evaluated OLIF combined with anterolateral fixation (OLIF-AF) versus unilateral biportal endoscopic lumbar interbody fusion (ULIF) in 107 patients with degenerative lumbar spondylolisthesis. The central result was that OLIF-AF showed superior restoration of lumbar sagittal parameters and earlier intervertebral fusion rates at 3 and 6 months postoperatively.