Venous thromboembolism (VTE) after intracerebral hemorrhage is well studied, but data on patients with spontaneous intraventricular hemorrhage (IVH) are limited. To study the factors associated with VTE, association between VTE and clinical outcomes in IVH, and safety of VTE chemoprophylaxis in IVH treated with intraventricular catheters and thrombolysis. Retrospective cohort study of patients enrolled in the CLEAR III trial, a multicenter, randomized trial comparing external ventricular drainage, with administration of intraventricular alteplase vs placebo, for obstructive IVH. Predictor variable was incident VTE in the first 30 d. Outcome measures were factors associated with VTE, and death/severe disability (modified Rankin Score 4-6) at 6 mo. Of the 500 patients with IVH, VTE occurred in 59 patients (11.8%) within the first 30 d. VTE chemoprophylaxis was initiated in 412 (82.4%) patients, but before VTE diagnosis in only 401 (80.2%) at median of 4 d (interquartile range, 1-8) from IVH onset, and was not associated with intracranial bleeding or catheter tract hemorrhage. In the multivariate logistic regression analysis, infection within 30 d (odds ratio, 1.80; confidence interval, 1.03-3.17) was significantly associated with higher odds of VTE occurrence. Starting VTE chemoprophylaxis after 72 h was additionally associated with VTE occurrence after the first week. Infection and delay in timely initiation of VTE chemoprophylaxis were associated with VTE occurrence. VTE chemoprophylaxis in IVH appears safe and should not be delayed beyond standard care policies for ICH including when intraventricular catheter placement and thrombolytic therapy are performed.