Childhood maltreatment can disturb brain development and subsequently lead to adverse socioemotional and mental health problems across the life span. The long-term association between childhood maltreatment and resting-wake brain activity during adulthood is unknown and was examined in the current study. Forty-one medically stable and medication-free military veterans (M = 29.31 ± 6.01 years, 78% male) completed a battery of clinical assessments and had [18F]-fluorodeoxyglucose positron emission tomography neuroimaging scans during quiet wakefulness. After statistically adjusting for later-life trauma and mental health problems, childhood maltreatment was negatively associated with brain activity within a priori defined regions that included the left orbital frontal cortex and left hippocampus. Childhood maltreatment was significantly associated with increased and decreased brain activity within six additional whole-brain clusters that included the frontal, parietal-temporal, cerebellar, limbic, and midbrain regions. Childhood maltreatment is associated with altered neural activity in adulthood within regions that are involved in executive functioning and cognitive control, socioemotional processes, autonomic functions, and sleep/wake regulation. This study provides support for taking a life span developmental approach to understanding the effects of early-life maltreatment on later-life neurobiology, socioemotional functioning, and mental health.