OBJECTIVE To investigate the frequency of persistent postoperative ptosis (PP) following trabeculectomy or Ahmed glaucoma valve (AGV) implantation and to analyze the associated factors. METHODS It is a prospective observational study on glaucoma patients who underwent trabeculectomy or AGV implantation from October 2015 to June 2017 in a tertiary center. Margin reflex distance 1 and 2 (MRD1 and 2) and levator function were measured before and at least 6 months, postoperatively. Clinically significant ptosis was defined as ≥2 mm drop of MRD1. RESULTS One hundred and fourteen patients (124 eyelids) including 76 patients (87 eyelids) with trabeculectomy and 35 patients (37 eyelids) with AGV implantation were included. The mean age was 55.50 (standard deviation = 17.54) years. Most of the surgeries were performed under general anesthesia (87.9%, 109/124) between 30 and 60 min (53.2%, 66/124) by residents (39.5%, 49/124). Trabeculectomy and AGV groups did not differ in terms of pre, intra, and postoperative variables (0.1≤ P ≤0.9) except duration of surgery (P = 0.01) and sex (P = 0.04). Clinically significant persistent PP was observed in 12.9% (16/124) in total, 13.7% (12/87) in the trabeculectomy group, and 10.8% (4/37) in the AGV group (P = 0.6). Male gender (ß coefficient = 2.56, 95% confidence interval (CI) = 4.76-0.36, P = 0.02) and a higher preoperative MRD1 (ß coefficient = 1.24, 95% CI = 0.52-1.95, P = 0.001) were the only factors affecting the frequency of clinically significant PP. CONCLUSIONS Postoperative blepharoptosis occurred in 12.9% of eyes after glaucoma procedures. Male gender and higher preoperative MRD1 were significantly associated with a higher frequency of postglaucoma surgery blepharoptosis.