Aim: Minimally invasive glaucoma surgery (MIGS) is not typically used in patients with advanced-stage glaucoma. This study describes the outcomes and complications of patients with advanced open-angle glaucoma (OAG) who underwent XEN implantation with cataract surgery or gonioscopy-assisted transluminal trabeculotomy (GATT) with cataract surgery. Methods: This retrospective study identified patients who had undergone XEN implantation or GATT for the management of advanced OAG. Outcomes included surgical success, intraocular pressure (IOP) reduction, number of topical IOP-lowering drops, visual field mean deviation (MD), best-corrected visual acuity (BCVA), and complications. Surgical success was defined as an IOP of <14 mm Hg and a 20% reduction at 12 months without topical IOP-lowering drops (complete success) or with topical IOP-lowering drops (qualified success). Results: Exactly 70 eyes were enrolled in this study, including 35 who had undergone XEN implantation and 35 who had undergone GATT. The overall surgical success rate was 74.3% (26 of 35) for eyes that underwent XEN implantation and 71.4% (25 of 35) for eyes that underwent GATT. Percent IOP reduction from baseline to 12 months postoperatively was 48% in the XEN cohort and 32% in the GATT cohort. Significant reduction in the use of topical IOP-lowering drops was demonstrated for both XEN (3.26 ± 1.15–1.23 ± 1.28) (p < 0.001) and GATT (2.46 ± 1.12–0.43 ± 0.78) (p < 0.001) cohorts at 12 months postoperatively. The only complication reported was transient hyphema, which occurred in three patients from the XEN group and four from the GATT group, and resolved spontaneously. Conclusions: Both XEN implantation and GATT may be safe and effective management options when treating patients with advanced OAG. However, larger sample sizes are required to make direct statistical comparisons between these techniques. Clinical significance: In this study, XEN implantation and GATT combined with cataract surgery were each associated with favorable outcomes in patients with advanced OAG.