OBJECTIVE: To determine risk factors for the occurrence of postoperative entrapped temporal horn (ETH), a specific form of isolated hydrocephalus that is a severe complication after resection of lateral ventricular trigone tumors, following trigone meningioma surgery. METHODS: A retrospective review was performed of 121 cases of trigone meningiomas surgically treated between November 2011 and March 2015 in Beijing Tiantan Hospital. Patient demographics, imaging features, surgical procedures, and postoperative complications were evaluated by statistical analysis. RESULTS: The median follow-up time was 24.1 months. Postoperative ETH developed in 23 patients (19.0%). Primary univariate analysis showed that young age, a longer clinical history, development of postoperative meningitis, and a longer duration of ventricular drainage were significantly associated with an increased risk of postoperative ETH. Subsequent multiple logistic regression analysis indicated that a clinical history of >3 months (odds ratio [OR], 4.8; P = 0.008), postoperative neurologic deficits (OR, 4.2; P = 0.014), duration of ventricular drainage >3 days (OR, 4.8; P = 0.012), and postoperative meningitis (OR, 9.9; P = 0.001) were independently associated with a risk of postoperative ETH. CONCLUSIONS: Postoperative ETH frequently occurs in patients with trigone meningiomas. The severity of surgical injury of the surrounding brain tissue partly accounts for the risk of postoperative ETH. Clinical management of ventricular drainage and postoperative meningitis are of utmost importance. Ventricular drainage should be performed on an individual basis, and drainage tubes should be removed as early as possible.