This study develops the evidence-base of interventions for inappropriate sexualised behaviour following brain injury involving adolescents. We describe a Single-Case Multiple Baseline Design intervention of Positive Behavioural Support (PBS) across settings. It involves a 16 year old adolescent who had a severe Traumatic Brain Injury (TBI) and presented with sexualised talk and touch. PBS may potentially be a successful intervention to remediate this. The aim of the article was to determine whether PBS could reduce the frequency and impact of the sexualised behaviour in a variety of his key daily settings. Visual and quantitative analyses were completed before and after the introduction of the PBS intervention within home and school settings. Findings showed reduction in the frequency of sexualised talk and touch alongside subjective impact ratings in the home. Downward trends were encouraging in the school settings, but demonstrated smaller effects than home. The Overt Behaviour Scale showed a reduction in overall severity and the impact on others. This study shows the promising impact on behaviour of introducing the PBS intervention within the home and school settings to support positive clinical change evidenced in the reduction in target behaviours and subjective response for caregivers.