Objective To investigate the risk factors associated with neovascular glaucoma (NVG) after pars plana vitrectomy (PPV) in eyes with proliferative diabetic retinopathy (PDR). Methods Retrospective study. One hundred and thirty-seven patients (137 eyes) with PDR who underwent PPV were recruited. There were 85 males and 52 females. The average age was (60.1±8.8) years old. The duration of diabetes was (10.2±3.6) years. There were 49 patients with ipsilateral carotid artery stenosis. Fifty-three eyes underwent intravitreal ranibizumab or conbercept injection before PPV. All eyes were treated with 23G standard three-port PPV. The average follow-up time after PPV was 11.5 months. Fundus fluorescein angiography (FFA) was conducted in postoperative 4-6 weeks to observe non-perfused retinal areas. Risk factors, such as ipsilateral carotid artery stenosis, the presence of non-perfusion in retina after PPV and the application of anti-vascular endothelial growth factor (VEGF) drugs before PPV, were identified by logistic regression. Results Twenty of 137 patients (14.6%) developed postoperative NVG after PPV. Ipsilateral carotid artery stenosis [odds ratio (OR) =5.048, 95% confidence interval (CI) 2.057-12.389,P=0.000] and the presence of non-perfusion in retina after PPV (OR=4.274, 95%CI 1.426-12.809,P=0.009) were significant risk factors for postoperative NVG, while the application of anti-VEGF drugs was not (OR=1.426, 95%CI 0.463-4.395,P=0.536). But the time from PPV to the onset of NVG varies significantly between the two groups of injection of anti-VEGF drugs or not (t=−4.370,P=0.000). Conclusions Risk factors associated with NVG after PPV in eyes with PDR included ipsilateral carotid artery stenosis and the presence of non-perfusion in retina after PPV. The application of anti-VEGF drugs before PPV can delay the onset of NVG in PDR eyes after vitrectomy.