--- - |2+ This pilot study explored acceptability to parents and outcomes for children of a preventive intervention for anxiety problems in pre‐schoolers with autism spectrum disorder (ASD) who were an identified sub‐group within a population‐based randomised trial of the Cool Little Kids parenting group programme. The population trial included 545 temperamentally inhibited pre‐schoolers recruited across eight economically diverse areas of Melbourne, Australia. Within this sample, 26 parents reported that their child had received an ASD diagnosis. Trial measures included baseline inhibited temperament and developmental problems, post‐intervention feedback on the programme, and caregiver‐reported child mental health outcomes (anxiety diagnoses and internalising symptoms) at 1‐ and 2‐year follow‐up. Sample retention for the children with ASD over 2 years was strong (92%). At follow‐up, fewer intervention than control children with ASD had anxiety disorders after 1 year (% (n): 25 (3) vs. 77 (10), P = .028) and separation anxiety symptoms after 2 years (M (SD): 4.22 (2.68) vs. 9.38 (5.91), P = .017). Similar effects favouring the intervention group were apparent across other child emotional outcome measures but without statistical significance in this small sample. Parents of the children with ASD reported that Cool Little Kids was “quite useful” in relation to their child's anxiety but also gave feedback that they would appreciate some tailoring of programme content to the context of ASD. These pilot findings suggest Cool Little Kids may be helpful for reducing comorbid anxiety in pre‐schoolers with ASD. Further research is warranted to develop an ASD‐specific adaptation which can be trialled with a larger sample of children with confirmed ASD diagnosis. Trial registration ISRCTN30996662 http://www.isrctn.com/ISRCTN30996662. Autism Res 2018. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. Lay Summary Many children with autism spectrum disorder (ASD) also have anxiety. This pilot study explored acceptability to parents and outcomes for pre‐schoolers with ASD of a parenting group programme to prevent anxiety problems. Among the sample of 26 pre‐schoolers with ASD, we found reduced anxiety disorders and separation symptoms when their parents had received the intervention, as reported by caregivers in checklists and clinical interviews. Parents gave feedback that the programme was useful but suggested content be adapted to the context of ASD. - Autism Research, EarlyView.