Background: Early intervention for autism spectrum disorder (ASD) tends to focus on enhancing social communication skills. We report data collected via focus group discussions as part of a feasibility and acceptability pilot randomized controlled trial (RCT) about a new parent group intervention to manage restricted and repetitive behaviours (RRB) in young children with ASD. Methods: The focus groups were led by two independent facilitators and followed a semi-structured topic guide with the aim of considering three key topics: experiences of participating in a RCT, opinions about the intervention and the impact of the intervention on the participants, their children and the family. Results: Fourteen participants attended the focus groups. Most participants reported that they had little knowledge of RRB before attending the intervention and that it had had a positive impact on them, their children and their family. Conclusion: The findings support the view that there is an unmet need for a parent-mediated intervention focusing on RRB.