Objective-To document the incidence of postoperative ocular hypertension (POH) after cataract surgery in dogs. Design-Retrospective analysis of medical records. Sample Population-88 dogs that had had cataract surgery. Procedure-The effect of several categorical variables on the development of POH was evaluated statistically. Postoperative ocular hypertension was defined as intraocular pressure > 25 and > 30 mm of Hg. Results-The incidence of POH > 25 mm of Hg was 48.9%; > 30 mm of Hg, 33.8%; > 40 mm of Hg, 20.1%; and > 50 mm of Hg, 5.8%. Mean onset of POH > 25 mm of Hg was 4.9 hours. The incidence of POH was not affected by the type of surgery. Eyes that had phacoemulsification developed POH significantly more rapidly (mean, 3.9 hours), compared with those that had extracapsular lens extraction (8.4 hours). Mean phacoemulsification duration was greater in eyes that developed POH, and older dogs were more likely to develop POH. Development of POH was not correlated with sex, stage of cataract, type of surgical procedure performed, intraocular lens placement, preoperative lens-induced uveitis, or posterior lens capsule tears and vitrectomy. However, eyes that received intraocular lens implants developed POH more rapidly, compared with eyes without implants. Clinical Implications-The high incidence and early onset of POH after cataract surgery suggests that routine use of antiglaucoma medications in the first 12 hours after surgery is warranted.