Purpose:To evaluate the efficacy of subconjunctival bevacizumab (ScB) as adjuvant therapy to primary trabeculectomy with mitomycin C (MMC) in primary open-angle glaucoma.Materials and Methods:Forty-six eyes of primary open-angle glaucoma patients were randomized to receive ScB (1.25 mg/0.05 mL) injections (the MMC+ScB group) at the end of the operations, or sham-treated controls (the MMC group). Intraocular pressure (IOP) was the primary outcome and secondary outcomes included bleb appearance, visual acuity, number of medications, complications, and proportion of eyes achieving successful outcomes at the 12-month follow-up.Results:Of 39 eyes, 20 eyes from the MMC+ScB group, and 19 eyes from the MMC group completed the follow-up. The mean postoperative IOP was 15.5±4.1 mm Hg in the MMC+ScB group (P<0.01; 40% reduction), and 14.7±4.3 mm Hg in the MMC group (P<0.01; 44% reduction). The differences in IOPs, at all follow-up visits, were not significant (P>0.05). The mean bleb vascularity score, at 1 month, in the MMC+ScB group was lower than the MMC group (1.55±0.51 vs. 2.26±0.6, respectively, P=0.01), but was not retained at follow-ups. The success rates at 12 months after surgery were 85% in the MMC+ScB group and 89.5% in the MMC group (P=0.53). The cumulative probabilities of surgical success were 80% and 73.7% in the MMC+ScB and in the MMC group, respectively (P=0.52).Conclusion:Single adjunctive ScB injection did not appear to have an additive benefit on outcomes of MMC trabeculectomy, in terms of IOPs and success rates.