Background: Emerging evidence supports the clinical impact of sleep disturbance (SD) on cancer patients. This study aimed to determine the prevalence and predictors of SD in people with malignant brain tumors and caregivers, and explore any relationship between the patient-caregiver dyad's sleep. Methods: Eighty-one adults with primary malignant (91%) or metastatic (9%) brain tumors and their family caregivers (nâ =â 44) completed a series of self-report questionnaires, including the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index, and the drowsiness item of The MD Anderson Symptom Inventory-Brain Tumor in an Australian ambulatory neuro-oncology setting. Participants were grouped by the PSQI cutoff (SDâ 5), and binary logistic regression analyses were performed to identify risk factors. Results: Of patients, 53% reported SD and 15% of those clinically significant insomnia, and 27% reported moderate to severe daytime drowsiness. Whereas anxiety, depression, fatigue, pain, neurocognitive symptoms, and antiemetic use were higher in patients with SD, fatigue and KPS were strong predictors of SD. In caregivers, 55% reported poor sleep and 13% clinical insomnia. Anxiety, caregiver burden, and comorbid illness were significantly associated with caregivers' SD. The individual's SD did not affect the chance of the other member of the patient-caregiver dyad experiencing SD. Conclusions: More than half the sample had sleep disturbance, which was linked to many concomitant symptoms, such as fatigue in patients and anxiety in caregivers, potentially contributing to distress and functional impairment. Understanding underlying mechanisms of SD, the potential use of these clinical predictors in care settings, and options for management is warranted.