Sleep is often disrupted in traumatic brain injury (TBI) and may be related to persistent behaviour problems; however, little is known about this relationship in young adults. This study explored associations between TBI, behavioural problems and sleep disturbances in 247 university students (197 non-TBI, 47 mild TBI, two moderate TBI, one severe TBI) aged 18-25 years, who completed validated measures for behaviour, sleep quality and history of TBI. Because of small group numbers, participants reporting moderate to severe TBI were excluded from the analyses. Results indicated that students with mild TBI reported higher levels of daytime dysfunction, somatic complaints, withdrawal, other behavioural complaints and internalizing behaviours compared with students with no TBI history. A correlational analysis indicated a moderate relationship between the above significant variables. Our results suggest that university students with a history of mild TBI are more likely to experience certain ongoing daytime behavioural problems, which are likely to negatively influence their academic functioning in tertiary education. This study highlights the importance of research on long-term problems following mild TBI in young adults aged 18-25 years--an age group often overlooked within the literature.