The main objective of this study is to describe the perception of 15 mothers of children with autism spectrum disorder (ASD) in regards to the impact of intensive behavioural intervention (IBI) on their children and their family. To achieve this goal, semi-structured interviews were held and descriptive forms were completed by mothers of children with ASD. Results show great influences on these children’s development as well as considerable effects on families as observed by participants. All mothers perceive the intervention positively. They indicate some inconvenients and make suggestions to help improve IBI.