Purpose <p>To evaluate the efficacy and safety of phacoemulsification combined with goniosynechialysis (phaco + GSL) in patients with acute primary angle-closure glaucoma (APACG) after failed trabeculectomy, complicated by refractory glaucoma and low corneal endothelial cell density (CECD).</p> Methods <p>Fourteen patients with APACG whose intraocular pressure (IOP) was uncontrolled after trabeculectomy were enrolled in this retrospective study. These patients also had a CECD &lt; 900 cells/mm². The patients were enrolled between August 2020 and June 2024. Preoperative and postoperative IOP, CECD, best-corrected visual acuity (BCVA), the number of IOP-lowering medications, anterior chamber depth, and postoperative complications were recorded.</p> Results <p>The mean CECD increased from 756.6 ± 106.2 cells/mm² preoperatively to 1138.18 ± 221.88 cells/mm² at 6 months postoperatively. Mean IOP decreased from 34.54 ± 10.61 mmHg preoperatively to 13.21 ± 2.51 mmHg postoperatively. The mean number of IOP-lowering medications decreased from 2.82 ± 1.47 to 0.09 ± 0.30 pre- and postoperatively, respectively. The mean time between trabeculectomy and phaco + GSL was 4.0 ± 3.61 months. Thirteen of the 14 eyes (92.86%) showed improved BCVA; one eye (7.14%) showed decreased BCVA because of associated retinitis pigmentosa. No corneal endothelial decompensation was observed. The mean anterior chamber depth increased from 1.47 ± 0.26 mm preoperatively to 2.81 ± 0.38 mm postoperatively. The mean extent of peripheral anterior synechiae decreased from 351.43° ± 24.78°–117.14° ± 23.30°</p> Conclusions <p>Early postoperative evaluation of CECD may not reflect the true corneal endothelial status in APACG. Even after failed trabeculectomy, with uncontrolled IOP and a CECD &lt; 900 cells/mm², phaco + GSL is an effective and safe approach to reduce IOP and the number of IOP-lowering medications and to partially improve visual acuity, with no serious complications.</p>