Background: To investigate the effect of percutaneous endoscopic lumbar discectomy (PELD) via a modified posterolateral approach on far lateral lumbar disc herniation (FLLDH) at L5/S1 level with high iliac crest. Methods: This retrospective study recruited the patients diagnosed of FLLDH at L5/S1 level with high iliac crest and accepted PELD in our hospital from March 2016 to November 2019. The visual analogue scale (VAS), Oswestry disability index (ODI), and modified Japanese Orthopaedic Association (M-JOA) scores were recorded before and after surgery. The fractional anisotropy (FA) values were recorded before and after operation. The incision length, operation duration, intraoperative blood loss, hospital stay and complications were observed. The excellent and good rate was calculated at final follow-up. Results: A total of 17 patients, including 10 males and 7 females, were screened and enrolled in this study. The mean incision length, operation duration, blood loss and hospital stays were 0.74±0.058 cm, 55.64±8.635 minutes, 27.42±4.936 ml, and 3.74±1.052 days, respectively. The postoperative VAS scores decreased, the ODI and M-JOA scores, and FA values of nerve root at affected side increased significantly (p<0.05), compared with those at pre-operation, but no difference was observed among the postoperative scores (p>0.05). The complications rate was 5.88% (1/17) and overall excellent and good rate was 94.12% (16/17) at the final follow-up. Conclusions: PELD via a modified posterolateral approach was an effective, minimally invasive and safe technique for FLLDH at L5/S1 level with high iliac crest.