Brain cancer represents a critical public health issue with thousands of newly diagnosed patients per year in Europe and the United States facing a dismal prognosis. The tumor immune microenvironment (TIME) has recently emerged as a key player promoting brain tumor growth and shaping responses to therapy. Consequently, new strategies have been developed to target the immune component of brain cancers and foster ant-tumoral immune responses, although they have only proven effective in a subset of patients. Therefore, it is of utmost importance to understand the dynamic biology of the TIME upon therapeutic intervention. Here, I describe different immunocompetent preclinical mouse models of primary and metastatic brain cancer, which allow a comprehensive exploration of the role of the immune system in tumor progression and response to therapy.