To evaluate the effect of intravitreal bevacizumab (IVB) on visual function and retinal thickness in patients with refractory diabetic macular edema (DME). Eyes with DME treated with IVB which were resistant to different previous treatments were enrolled in this retrospective, non-randomized series study. Each patient underwent a complete ophthalmic examination including best-corrected visual acuity (BCVA), slit-lamp examination, intraocular pressure measurement, fundus examination, retinal thickness measurement with optic coherence tomography at baseline and at each visit. Digital fundus fluorescein angiography was performed at baseline for each patient. A total of 71 eyes of 59 patients (36 male and 23 female) were included in the study. All eyes had focal laser photocoagulation (71 eyes, 100 %) and had one other additional treatment including an intravitreal (23 eyes, 32 %) or subtenon (18 eyes, 25 %) injection of triamcinolone acetonide. The mean follow-up period was 9.79 ± 8.6 months and the mean number of IVB treatments was 2.01 ± 1.06 (min-max, 1-4). Mean logMAR BCVA was 0.88 ± 0.4 at baseline, 0.78 ± 0.4 at 4 weeks and 0.79 ± 0.4 at the last visit (p = 0.036). The mean central foveal thickness was 515.4 ± 150.3 μm at baseline which significantly decreased to 367.01 ± 166.6 μm at 4 weeks (p = 0.0001) and 338.1 ± 159.7 μm at the last visit (p = 0.0001). Sixteen percent of the eyes did not respond to IVB treatment. IVB treatment for refractory DME seems to be effective and safe and repeated treatments are necessary for a significant portion of the cases.