Background Little is known about the experiences of parents whose sons or daughters are diagnosed with autism spectrum disorder (ASD) during adulthood.

Method In this exploratory study, 6 mothers of adults recently diagnosed with ASD were interviewed about the ASD assessment process. Thematic analysis was used to analyse the interviews.

Results Two superordinate themes are described: (1) biographical continuity, and (2) biographical disruption. Mothers did not experience significant disruption around the ASD assessment itself, as they had sought an explanation for their son’s/daughter’s behaviour since childhood. Therefore, being referred for an ASD assessment was simply another assessment for their son or daughter and was thus a biographical continuity. Mothers experienced biographical disruption once an ASD diagnosis was received, as they realised that an ASD diagnosis did not result in any additional support, and found this greatly frustrating.

Conclusions There is an unmet need for postdiagnostic support among adults diagnosed with ASD, and for their parents.