Purpose: The aim of this study was to evaluate the effect of adding intraoperative aflibercept injection to preoperative injection in optimizing the anatomical and functional outcomes of diabetic vitrectomy compared to preoperative injection only. Patients and methods: This retrospective interventional comparative study included 30 eyes of 30 patients scheduled for pars plana vitrectomy for complications of proliferative diabetic retinopathy. The patients were allocated into two groups: group I that received combined preoperative and intraoperative aflibercept (Eylea) injection and group II that received preoperative injection only. Best-corrected visual acuity (BCVA) and central macular thickness (CMT) were compared preoperatively and 3 months postoperatively in both groups. The patients were also followed up to detect any postoperative persistent vitreous hemorrhage (VH) or sub-silicone hemorrhage. The patients who developed persistent nonclearing VH for more than 1 month or persistent nonclearing sub-silicone premacular hemorrhage were scheduled for surgical reintervention. Results: The mean preoperative BCVA was 1.53±0.28 LogMAR in group I and 1.50±0.26 LogMAR in group II. At the end of the third postoperative month, there was a continuous significant improvement in BCVA in both groups with a mean of 0.31±0.10 in group I and 0.62±0.26 in group II, with a statistically significant difference between the two groups (P<0.0001). The baseline CMT was measured within 1–3 weeks postoperatively with a mean of 393±31.54 μm in group I and 379.3±40.42 μm in group II. Three months postoperatively, the CMT significantly decreased to 206±12.94 μm in group I and 301.67±48.6 μm in group II with a statistically significant difference between the two groups (P<0.0001). Postoperative persistent VH occurred in three eyes out of the six (50%) air-filled eyes in each group, while three eyes out of the eight (37.5%) silicone-filled eyes in group I and six (60%) eyes out of the 10 silicone-filled eyes in group II developed postoperative sub-silicone hemorrhage. Only one (12.5%) case in group I and five cases in group II required surgical reintervention due to persistent sub-silicone hemorrhage. Conclusion: Combined preoperative and intraoperative aflibercept injection compared to preoperative injection alone was more effective in optimizing the anatomical and functional outcomes and in reducing the possible postoperative complications after pars plana vitrectomy.