Deep venous thromboses (DVT) and venous thromboembolisms (VTE) are serious complications after neurosurgical procedures. Hemorrhagic complications of thera-peutic anticoagulation on the other hand are also highly dreaded due to the high risk of permanent neurological deficit. Clear guidelines concerning dosage and duration of anticoagulation still do not exist for neurosurgical practice. Over a 10-year episode, patients with postoperative DVT or VTE were retrospectively identified and demographic risk factors as well as routine laboratory coagulation parameters were assessed. The goal was to determine patients at risk for a severe course of thrombosis and complications due to anticoagulation. In total, 173 patients with DVT or VTE were identified. Clinical effect of thrombosis was severe in 32.4% and fatal in 5.8% of all patients. Spinal surgery was associated with a higher risk of major or fatal outcome of thrombosis as compared to cranial procedures (fatal: 12.1 vs. 4.3%, p = 0.035). Elevated partial thromboplastin time, low platelet levels and low quick on diagnosis of thrombosis were associated with a fatal clinical course (p = 0.02, 0.04 and 0.02 respectively). Severe hemorrhagic complications on the other hand occurred in 6.6%, 0.6% were fatal. D-dimer did not predict the course of DVT/VTE but higher levels of D-dimer on day 3 after diagnosis of DVT/VTE were associated with a higher risk of severe bleeding complications (cutoff 4.95 µg/mL). Partial thromboplastin time after initiation of anticoagulation was not associated with hemorrhagic complications and might thus be not helpful to determine the risk of bleeding complications during the early postoperative phase. D-dimer might be of additional use to detect early bleeding complications.