Objectives. To describe levels of traumatic childhood events in a sample of homeless individuals and to assess the contribution of traumatic events to neurobehavioural traits (measured with the Frontal Systems Behaviour Scale, FrSBe) and general cognitive function (IQ). Design. A sample of 55 homeless adults was recruited from homeless services in the city of Sheffield, UK. All were interviewed to acquire substance misuse information, record experiences of childhood trauma, and assess cognitive and neurobehavioural traits. Methods. Experiences of abuse and neglect were assessed with the Childhood Trauma Questionnaire. Participants also completed the Wechsler Abbreviated Scale of Intelligence and the FrSBe, which was completed with respect to current behaviour and conduct prior to homelessness. Results. Around three-quarters of the sample scored in the clinically significant range for current neurobehavioural impairment. They also reported high levels of impairment when rating retrospectively for the period before they were homeless. The mean group IQ was below average at 88. Abuse or neglect during their upbringing was reported by 89% of the sample. Emotional abuse, emotional neglect, and physical neglect were all positively correlated with total FrSBe scores. Sexual abuse, emotional neglect, and physical neglect were all negatively correlated with IQ. The associations between trauma and IQ and neurobehavioural traits appear generally unrelated to the presence of substance misuse in the sample. Conclusion. Our homeless sample displayed relatively low IQ with high levels of neurobehavioural impairment. Our evidence suggests that these neuropsychological factors may, in part, constitute a long-term consequence of childhood trauma.