Background and objectives: Sleep disturbances are frequently reported in children with brain tumours. The objective of our cross-sectional study was to systematically examine sleep in these children. We hypothesised that children with tumours involving the sleep-wake-regulatory areas have an altered sleep-wake-regulation. Methods: Sixty-one patients aged 0–18 years and with a diagnosis of a primary brain or cervical medullary tumour were included. They were categorised based upon tumour location into two groups – those affecting the sleep-wake regulatory regions, i.e. brain stem, basal forebrain, hypothalamus, thalamus, and posterior fossa compressing the brain stem and those that did not. Sleep history, questionnaire surveys, polysomnography, and multiple sleep latency test were used, as indicated clinically. Surveys included Pediatric Daytime Sleepiness Scale, Children's Sleep Habits Questionnaire, Strengths and Difficulties Questionnaire, and Pediatric Quality of Life Inventory, Multidimensional Fatigue Scale and Generic Core Scale. Results: Patients with tumours involving the sleep-wake regulatory areas were sleepier/more fatigued (p = 0.03). Sleep apnoea was observed in 86% of all the patients and comorbid narcolepsy in 8%, without group differences (p ≥ 0.12). Patients with tumours involving the sleep-wake-regulatory areas had more emotional problems (p = 0.04), were more affected by mental health problems (p < 0.001), and had poorer quality of life (p ≤ 0.03). Conclusions: Many children with brain tumours suffer from disturbed sleep, poor mental health, and low quality of life. We recommend that systematic sleep evaluation is included in their routine care along with psychological and social support.