Purpose: To evaluate the effect of intravitreal bevacizumab (IVB) injection on central macular thickness (CMT) in patients with diabetic macular edema (DME) associated with epiretinal membrane (ERM) and compare the results to those with DME without ERM.Methods: 54 eyes of 54 patients with DME were included in this prospective comparative case series. Twenty-eight patients had ERM. All patients received 2.5 mg/ 0.1 ml IVB. The primary outcome measure was the change in central macular thickness (CMT) and the secondary outcome measure was the change in best corrected visual acuity (BCVA), one month after the IVB injection.Results: All the patients completed 1-month follow-up. One month after the IVB injection, there was no statistically significant reduction in terms of CMT for the ERM group (22.64 ± 70.1 μm; P = 0.099), unlike eyes with DME alone (60.34 ± 88.5 µm; P = 0.002). Patients with ERM had a -0.09 ± 0.14 log MAR improvement in their BCVA (P =0.001) vs. 0.03 ± Log MAR change in the patients who did not have ERM (P = 0.37).Conclusion: In this study, intravitreal bevacizumab resulted in improvement in BCVA in patients who had DME associated with ERM. However, in patients who only had DME, despite a reduction in CMT, no improvement in BCVA occurred. Future randomized clinical trials are warranted to precisely assess the effect of bevacizumab on the ERM.