Objective: With advances in endoscopic surgery, L5–S1 foraminotomy has become a readily accessible surgical technique. However, symptom relief is often short-lived, and recurrence is common. As an alternative, biportal endoscopic fusion at L5–S1 can improve symptoms. However, it can be challenging and may lead to fusion-related complications. Therefore, we aimed to compare 2 procedures for L5–S1 foraminal stenosis. Methods: A total of 37 patients diagnosed with L5–S1 foraminal stenosis were divided into 2 groups for this study. Group 1, comprising 18 patients, underwent L5–S1 foraminotomy via a paraspinal approach from 2017 to 2019. Group 2, comprising 19 patients, underwent biportal endoscopic L5–S1 fusion with the facet-sacrificing approach from January 2021 to August 2023. A comprehensive evaluation of both groups was conducted using various metrics, including image findings, operation time, hospital stay, visual analogue score (VAS) back, VAS leg, Oswestry Disability Index (ODI), and the MacNab criteria. Postsurgical complications were meticulously recorded. The statistical analysis was performed using the Wilcoxon signed-rank test, and differences between the 2 surgical approaches were assessed using the Mann-Whitney U-test. Results: No statistically significant difference was found in VAS back or ODI improvement between the 2 groups. However, the foraminotomy group exhibited a statistically significant advantage in terms of operation time and hospital stay. Conversely, the fusion group demonstrated statistically significant improvements in VAS leg and McNab criteria in comparison to the foraminotomy group. The most prevalent complication observed in the foraminotomy group was early symptom recurrence, while the fusion group experienced complications related to screw-related issues and infections. Conclusion Leg symptoms recurred more frequently in the foraminotomy group. Biportal endoscopic facet-sacrificing transforaminal lumbar interbody fusion surgery has been demonstrated to be a valuable technique for L5–S1 fusion with lower recurrence of leg symptoms; however, it is associated with complications specific to fusion.