Precis: The present study demonstrates that surgical success rates of gonioscopy-assisted transluminal trabeculotomy (GATT) with a target intraocular pressure (IOP)<= 21 mm Hg are 93.3% (for qualified success) and 26.7% (for complete success) in vitrectomized patients exhibiting secondary open-angle glaucoma (SOAG) after silicone oil (SO) removal, for an average follow-up of 37.5 months. Purpose: To report the long-term outcomes of GATT in vitrectomized patients exhibiting SOAG after SO removal. Setting: Retrospective case-series study. Patient Population: This retrospective case-series study enrolled vitrectomized patients who underwent uneventful GATT surgery between May 2014 and May 2019 at Gazi University Hospital for the treatment of medically uncontrolled SOAG after SO removal. Main Outcome Measures: At baseline and at each postoperative visit, a detailed ophthalmic examination consisting of slit-lamp biomicroscopy, indirect ophthalmoscopy, macular optical coherence tomography, and Goldmann applanation tonometry was performed in all patients. Baseline demographic and clinical characteristics, duration between pars plana vitrectomy and SO removal, duration between SO removal and onset of SOAG, follow-up time, need for antiglaucoma medication, visual acuity, and IOP measurements were noted. Surgical success was defined as an IOP <= 21 and >= 6 mm Hg with (qualified success) and without (complete success) IOP-lowering medication. Results: A total of 15 patients had a history of pars plana vitrectomy with 1000 centistoke SO tamponade before the GATT surgery. GATT was performed in all patients with SOAG after SO removal. The mean age and follow-up of the patients were 53.6 +/- 11.8 years (range, 34 to 72 y) and 37.5 +/- 15.1 months (range, 12 to 61 mo), respectively. The average duration of SO tamponade in the vitreous cavity was 7.5 +/- 1.6 months (range, 5 to 10 mo). The average duration between the SO removal and the development of SOAG was 14.1 +/- 13.2 months (range, 2 to 46 mo). The mean IOP decreased from 31.0 +/- 4.1 mm Hg at baseline to 15.6 +/- 4.6 mm Hg at final visit. The mean final logMAR BCVA was 0.92 +/- 0.58 (range, 2 to 0.045). Qualified surgical success was achieved in 14 (93.3%) patients, whereas complete success was achieved in only 4 (26.7%) patients (P<0.001). Conclusions: GATT seems to be safe and successful procedure for controlling IOP in patients exhibiting SOAG after SO removal. However, most patients may require antiglaucoma medication during the follow-up, particularly within the first 2 postoperative years.