Non-invasive measurement of intracranial pressure (ICP) reduces the complications and cost for both patient and health care systems. Improvement of non-invasive methods has led to development of systems for reproducing continuous, real-time non-invasive ICP signals. So far, non-invasive methods have been tailored for the patients with head trauma. We have used Schmidt’s auto-adaptive method to assess the accuracy of this method for patients after surgery for supratentorial brain tumors. Data from forty patients with the diagnosis of brain tumor operated from 2008 to 2010 were used to estimate the accuracy of Schmidt’s method in our patients. We obtained the model parameters from 30 recordings. We determined the ICP wave form for the remaining patients by both invasive and non-invasive techniques. In the test group, by invasive method, the mean ICP±2SD was 17.1 ± 6.6 mmHg and using non-invasive method, the mean ICP ± 2SD was 16.5 ± 5.4 mmHg. The calculated error was 4.6 mmHg using root mean square errors. The average Pearson correlation between the estimated and real waveforms was 0.92. We believe that application of this method is acceptable for post-operative assessment of ICP in brain tumor patients.