Diagnosis of a brain tumor is made by a doctor or medical professional. Different Symptoms may provide clues leading toward the diagnosis of a brain tumor, but there is no clinical symptom.

Imaging is often used for diagnosis of brain tumors, with the common methods being computed tomography (CT scan) an magnetic resonance imaging (MRI). Previous methods included pneumoencephalography and cerebral angiography, but they have been largely discarded recently due to their invasive and potentially dangerous natures.

Electroencephalography (EEG) and other eletrophysiological exams may be used in the process of brain tumor diagnosis, as well.

Confirmation for a brain tumor diagnosis may be given by a histological examination of tissue from the tumor. This examination is necessary for learning the proper treatment method and prognosis.