OBJECTIVE To compare rates of early postoperative hypotony and intraocular pressure (IOP) elevation between 23-gauge sutureless vitrectomies with and without phacoemulsification and intraocular lens implantation in patients with proliferative diabetic retinopathy. METHODS This study reviewed the medical records of 302 eyes of patients who underwent primary 23-gauge sutureless vitrectomy for the complications of proliferative diabetic retinopathy. A case series of 207 eyes that underwent combined vitrectomy and cataract surgery (combined group) was compared with that of 95 eyes that underwent vitrectomy only (vitrectomy group): The eyes that remained phakic after the vitrectomy were excluded from this study. The main outcome measures were postoperative hypotony (IOP < 6 mmHg or IOP < 10 mmHg with choroidal detachment) and IOP elevation (>30 mmHg). RESULTS Postoperative hypotony was identified in 4 (1.9%) of 207 eyes in combined group, but in 7 (7.4%) of 95 eyes in vitrectomy group (P = 0.048). Rate of IOP elevation was very low and not different between the two groups. The multivariate analysis showed that vitrectomy without cataract surgery was associated with the postoperative hypotony (odds ratio = 4.6, P = 0.045). CONCLUSIONS The incidence of early postoperative hypotony was lower in combined sutureless vitrectomy and cataract surgery than in sutureless vitrectomy alone and that of IOP elevation was very low in both groups. The maintenance of a stable IOP with a low risk of IOP fluctuation may be an additional advantage of sutureless diabetic vitrectomy combined with cataract surgery.