Traumatic brain injury (TBI) is a leading cause of death and disability for children and young people worldwide. Research has found that children in infancy and early childhood are at the highest risk of sustaining a TBI; and that mild TBI accounts for a large majority of these injuries. Unfortunately, there is limited research regarding the effects of TBI in this age group; and population-based studies are undertaken rarely. Most of the paediatric TBI research also focuses on school-aged children; and thus the effects of TBI sustained in infancy are not yet well understood. The main aim of this study was to investigate whether preschool children who have sustained a mild TBI would perform differently to healthy children in executive function (EF), with a particular focus on working memory and inhibitory control. A secondary aim was to investigate whether preschool children who have sustained a mild TBI would differ to healthy children in behavioural/emotional functioning. The investigation involved a population-based sample of 24 children who sustained a mild TBI between the ages of 0-2 years old. 24 children who had not had a TBI were also recruited as an age-matched comparison group. Assessments involved both parents and their children; and were conducted approximately 24 months post-injury. Parents completed the Behaviour Rating Inventory of Executive Function – Preschool Version (BRIEF-P); and the Behaviour Assessment System for Children, Second Edition (BASC-2). Children were also assessed using performance-based measures of EF such as the Delayed Alternation task - which measures working memory; and the Colour-Object Interference task - which measures inhibitory control. Results showed that children with and without mild TBI were characterised by similar EF abilities, including working memory and EF behaviours. In contrast, more children in the injury group (22.7% of the TBI sample) had clinically significant internalising behaviour problems (anxiety, depression and somatisation) as rated by their parents. These results indicate the need for children who have had a mild TBI to be screened for possible behavioural/emotional difficulties; and for interventions to be implemented as needed. Additional support for parents/caregivers may also be necessary. While no differences were observed between the two groups in EF at the time of assessment, it is recommended that longer-term studies are conducted.