In South Africa, many learners with autism spectrum disorder (ASD) attend mainstream and private schools. This study explores the influence of executive function (EF) challenges experienced by one learner with ASD on his behavioural adaptation in an inclusive school environment. An interpretive case study approach was followed to help understand one unique ASD learner and explain the complexity of the behavioural adaptation challenges that he was experiencing. Observations and an interview were used as data collection methods. During data analysis, themes were identified within each section of the transcript. The processes of coding and categorising were employed to find connections and similarities between all the data collected. The results indicate that Learner T experienced EF challenges. Without acquiring and implementing appropriate EF skills, he found it difficult to exhibit appropriate social behaviour in the inclusive learning environment. The study attempts to debunk misconceptions people may have regarding the behavioural adaptability of ASD learners in an inclusive school environment.