The transition from primary to secondary school is a stressful period for autistic individuals. However, less is known about parental experiences of the school transition, and its impact on the family. This study explored mothers' perspectives on the psychological impact of the transition to secondary school for their autistic children and their families. Using Interpretative Phenomenological Analysis, semi-structured interviews were analysed to explore the experiences of eight mothers of autistic children at the end of their child's first year in secondary school. The analysis revealed two superordinate themes: lack of available support and detrimental psychological impact on the family. Mothers reported the negative impact the transition had on themselves, their child, and the wider family. The importance of pre- and ongoing transition support was highlighted to reduce the concerns of children and their parents throughout the transition process. The findings highlighted the need for autism-specific individualized guidance, as well as considering the potential for transition issues to impact on siblings.