The NCCN Clinical Practice Guidelines in Oncology for Central Nervous System Cancers use radiologic presentation in the initial evaluation of patients with primary brain tumors and in the determination of response to therapy. The dominant modality use is MRI because of its superior image resolution, speed of acquisition, and high safety profile for patients. The interpretation of MRI is a critical aspect of patient care and evaluation. This article reviews the predominant aspects of MRI for brain tumors, the standard sequences, the criteria to consider in determining treatment response, and advanced aspects currently available. The proper integration of this essential imaging modality into patient care ensures timely disease evaluation and guides the use of therapeutic tools.