OBJECTIVE Surgical decompression via a posterior interlaminar approach is widely used for treating lumbar central canal stenosis (LCCS). However, this surgical approach poses a challenge for elderly patients with comorbidities. Thus, the authors tried a new surgical decompression via the unilateral intervertebral foraminal approach with local anesthesia to treat such patients. The aim of this study was to evaluate the safety and effectiveness of surgical decompression via the unilateral intervertebral foraminal approach with local anesthesia for patients with LCCS. METHODS Patients with LCCS who underwent surgical decompression, performed by a single surgeon, between January 2016 and March 2019 were retrospectively analyzed. All patients received decompression via the unilateral intervertebral foraminal approach with local anesthesia. Visual analog scale (VAS) scores, Oswestry Disability Index (ODI) scores, modified Macnab criteria, walking distance, and Schizas classification were used as outcome predictors. Additionally, a decompression evaluation method was designed for use after spinal endoscopic surgery. RESULTS Overall, 23 patients with a mean age of 69 years were included in this study, with a mean follow-up of 28 months. Low-back and leg pain were significantly improved after decompression surgery. Postoperative ODI scores and walking distances were statistically significantly better than before surgery. Postoperatively, the Schizas classification for all patients was improved by at least 1 grade compared with the preoperative grade. No complications occurred during the follow-up period. According to the novel decompression evaluation method, all patients had at least achieved decompression in part 123+B. CONCLUSIONS Surgical decompression via the unilateral intervertebral foraminal approach with local anesthesia showed promising outcomes in the treatment of elderly patients with LCCS. Additionally, a proposed postoperative decompression evaluation method can help guide surgical decompression.