To evaluate the efficacy and safety of bevacizumab monotherapy or combined with laser versus laser monotherapy in Mongolian patients with visual impairment due to diabetic macular edema.Prospective, randomized, single-center, a 12 month, laser-controlled, clinical trial. Participants: One hundred twelve eligible patients, aged ≥18 years, with type 1 or 2 diabetes mellitus and best corrected visual acuity (BCVA) in the study eye of 35 to 69 Early Treatment Diabetic Retinopathy Study (ETDRS)letters at 4 m (Snellen equivalent: ≥6/60 or ≤6/12), with visual impairment due to center-involved diabetic macular edema (DME). Methods: Patients were randomized into three treatment groups:(I) intravitreal bevacizumab monotherapy (n=42), (II) intravitreal bevacizumab combined with laser (n=35), (III) laser monotherapy (n=35). Bevacizumab injections were given for 3 initial monthly doses and then pro re nata (PRN) thereafter based on BCVA stability and DME progression. The primary efficacy endpoints were the mean change in BCVA and central retinal subfield thickness (CRST) from baseline to month 12.Bevacizumab monotherapy or combined with laser were superior to laser monotherapy in improving mean change in BCVA letter score from baseline to month 12 (+8.3 and +11.3 vs +1.1 letters; both p<0.0001). There were significant difference detected between the bevacizumab and bevacizumab combined with laser treatment groups (p=0.004). At month 12, greater proportion of patients gained ≥10 and ≥15 letters and with BCVA letter score >73 (Snellen equivalent: >6/12) with bevacizumab monotherapy (23.8% and 7.1% and 4.8%, respectively) and bevacizumab + laser (57.1% and 28.6% and 14.3%, respectively) versus laser monotherapy. The mean central retinal subfield thickness was significantly reduced from baseline to month 12 with bevacizumab (−124.4 μm) and bevacizumab + laser (−129.0 μm) versus laser (−62.0 μm; both p<0.0001). Conjunctival hemorrhage was the most common ocular events. No endophthalmitis cases occurred.Bevacizumab monotherapy or combined with laser showed superior BCVA improvements over macular laser treatment alone in Mongolian patients with visual impairment due to diabetic macular edema.