This study aims to describe the feasibility of inserting an oblique lumbar interbody fusion (OLIF) cage through biportal endoscopic lumbar interbody fusion (BE-LIF) and to illustrate the key surgical steps through a case-based video demonstration. BE-LIF is a safe and effective minimally invasive fusion technique. Among the factors influencing successful fusion, the cage footprint plays a critical role—a larger cage increases endplate contact area, maintains disc height, and enhances segmental stability. The OLIF cage offers these biomechanical advantages; however, inserting it through a biportal endoscopic approach is technically demanding and requires several strategic considerations. These include meticulous preoperative planning of portal positions to optimize visualization and working angles, adequate preparation of the disc space window for cage insertion, precise endplate preparation, and safe neural manipulation within a confined surgical field. A 56-year-old female presented with chronic low back pain and bilateral leg symptoms unresponsive to conservative treatment. Imaging revealed severe L4–5 central canal stenosis, foraminal narrowing, and instability. She underwent BE-LIF with OLIF cage insertion and percutaneous pedicle screw fixation. The step-by-step surgical video demonstrates portal placement, decompression, endplate preparation, bone grafting, and cage insertion under combined endoscopic and fluoroscopic guidance. The operation lasted 180 minutes, with an estimated blood loss of 150 mL. The patient was mobilized on postoperative day 1 and discharged on day 5 with marked improvement. Follow-up radiographs confirmed restoration of disc height, correct cage positioning, and adequate decompression. This case demonstrates that BE-LIF with OLIF cage insertion is feasible and may enhance fusion potential by combining the minimally invasive benefits of biportal endoscopy with the biomechanical advantages of a large-footprint cage. However, the procedure remains technically demanding and is best suited for experienced endoscopic spine surgeons.