Purpose: The vitamin E compound α-tocopherol inhibits fibroblast growth in vitro. To evaluate its potential benefit in preventing failure of glaucoma filtration surgery, we prospectively investigated the outcome of filtering surgery with postoperative dietary α-tocopherol supplementation. Patients and Methods: Thirty-nine patients (39 eyes) with primary open-angle glaucoma or pseudoexfoliative glaucoma were randomly assigned to two post-(phaco)-trabeculectomy treatment groups. Daily oral intake of 300 mg α-tocopheryl-acetate (absorbed as α-tocopherol in the intestine) for 2 months was compared to a placebo preparation in a double-blind trial. The follow-up time was 1 year. Success was defined as intraocular pressure (IOP) ≤18 mm Hg with no medication, no needling revision, and no subconjunctival injection. Results: In the tocopherol group, the relative risk for trabeculectomy failure decreased from 1.58 at 2 weeks (p = 0.95) to 1.0 at 1 year. Success rates (67–90%) and IOP reduction (mean 39 to 53%) were statistically comparable in the two groups. Considering postoperative complications, no relevant differences were found. Discussion: Trabeculectomy and phacotrabeculectomy outcome did not show any differences between α-tocopherol-supplemented patients and the placebo group.