Radiation is standard-of-care treatment for primary brain tumors but may have profound effects on sleep that have not yet been fully characterized. This systematic review aims to further our understanding of radiation therapy on risk of development of sleep disorders in patients with primary brain tumors (PBTs), as well as potential opportunities for prevention and treatment. A systematic search of PubMed, Embase, and Web of Science was performed (last Jan 2024) with predefined inclusion (PBT patients, radiation therapy, somnolence/circadian disruption) and exclusion (reviews/abstracts/cases/chapters, non-PBT cancer, lack of radiation) criteria, yielding 267 papers initially and 38 studies included. Data extraction and analysis (descriptive statistics, individual study summary) focused on incidence of sleep disturbances, radiation types/doses, and pharmacologic interventions. Risk of bias assessment was conducted with Effective Public Health Practice Project's Quality Assessment Tool for Quantitative Studies. The included 38 studies (n=2948 patients) demonstrated high incidence of sleep disturbances in patients with primary brain tumors throughout radiation therapy, but primarily from the end of radiation to 6 months after. Sleep symptoms were associated with radiation (dose-dependent), and pharmacotherapies were helpful in patients with formal sleep disorder diagnoses. Terminology and incidence reporting of sleep symptoms are inconsistent, and many studies had high risk of bias. This systematic review highlights the ongoing challenges with sleep symptoms/disorders related to cranial irradiation treatment in the primary brain tumor population. Further investigations on the interconnectedness of sleep disturbance constructs and possible pharmacotherapies to alleviate symptoms are warranted.