AIM: To evaluate the effect of intravitreal bevacizumab (IVB) injection 1 week before pars plana vitrectomy (PPV) in proliferative diabetic retinopathy (PDR) patients. METHODS: A retrospective research was done on 46 PDR patients who were divided into PPV group (n=28) and IVB group (n =18, PPV with preoperative IVB). Bevacizumab was injected 1 week before PPV. Main outcome measures were visual acuity, incidence of iatrogenic retinal breaks, intraoperative and postoperative bleeding. RESULTS: At 1 month after surgery, visual acuity in PPV (82.1%) and IVB group (88.9%) improved significantly (P＜0.01) and the difference between the two groups was not significant (P＞0.05). Iatrogenic retinal breaks were reported in 18 cases (64.3%) in PPV group and 4 cases (22.2%) in IVB group (P＜0.05). Intraoperative bleeding was encountered in all cases in PPV group and 7 cases (39%) in IVB group (P＜0.01). Postoperative bleeding was reported in 9 cases (32.1%) in PPV group and none in IVB group (P＜0.01). CONCLUSION: IVB injection before PPV is helpful in reducing iatrogenic retinal breaks, intraoperative and postoperative bleeding in PDR patients.