Objective: To identify the potential risk factors for proliferative diabetic retinopathy (PDR) in cases with early postoperative vitreous hemorrhage (PVH) after 23-gauge vitrectomy. Methods: In this case-controlled study, the medical records of 69 eyes of 69 consecutive PDR patients who underwent primary 23-gauge vitrectomy During January 2014 to December 2016 at Eye Hospital, China Academy of Chinese Medical Sciences were reviewed. The eyes were divided into two groups, one with early PVH(19 cases) and the other without it (50 cases). Demographic data and ocular and systemic parameters were analyzed. Differences between the two groups in the clinical characteristics of the ocular and systemic factors were determined using t-tests or chi-square tests. Risk factors for development of early PVH were determined by Logistic regression analysis. Results: The overall incidence of early PVH was 28% (19/69 eyes).The mean±standard deviation age of the patients with and without early PVH were 49.6±8.7 years and57.3±10.0 years respectively (t=-2.969, P=0.040). There were no significant differences in any of the other systemic factors. The values for the early PVH group were all greater than for the non-early PVH group for the following parameters: lens status (crystalline lens/intraocular lens) (χ2=3.933, P=0.047), preoperative intravitreal anti-vascular endothelial growth factor injection (χ2=4.784, P=0.029), fibrovascular membrane
proliferation (χ2=8.180, P=0.004), and intraoperative bleeding from new vessels on the disc (χ2=11.147,P=0.001). There were no significant differences in other ocular factors. The risk factors associated with the incidence of early PVH were bleeding from new vessels on the disc (OR=6.249, P=0.012) and fibrovascular membrane proliferation (OR=4.833, P=0.028). Conclusions: Early PVH after 23-gauge vitrectomy tends to occur in severe PDR cases. Bleeding from new vessels on the disc and fibrovascular membrane proliferation increase the risk of early PVH.