This study aimed to investigate the feasibility, acceptability, and preliminary effects of an acceptance and commitment therapy (ACT)-based parenting program for parents of autistic children. A pilot randomized controlled trial (RCT) was conducted, with 40 parents randomly assigned to either the eight-session ACT-based parenting program or usual care. Feasibility was assessed by the rates of recruitment, attritions, and adherence to the intervention. Acceptability was evaluated through participant satisfaction surveys and semi-structured group interviews. Intervention feasibility was established with very satisfactory recruitment, attrition, and intervention completion rates. Both participant satisfaction survey and qualitative interviews suggested that the intervention was acceptable and beneficial for parents of autistic children. Compared to the usual-care-only group, participants in the ACT-based parenting program showed significant improvements in parental stress, depressive symptoms, anxiety symptoms, psychological flexibility, self-efficacy, and reductions in emotional and behavioral problems in their children at the immediate post-intervention assessment. These findings support the feasibility, acceptability, and preliminary effectiveness of the ACT-based parenting program for parents of autistic children. Future larger-scale RCTs can be conducted with longer-term follow-ups and more comprehensive assessment of its effectiveness for family caregivers of diverse groups of autistic children and/or other neurodevelopmental conditions.Lay abstractThis study aimed to examine whether an acceptance and commitment therapy (ACT)-based parenting program, incorporating topics of emotional and stress management, parenting skills training, autism-related education, and self-care learning, could be successfully implemented, well-received, and beneficial for parents of children with autism. We randomly assigned 40 parents to either participate in the eight-session ACT-based parenting program or receive usual care only. The program was found to be feasible, with many parents willing to participate and complete the sessions. The parents also reported high satisfaction with the program and found it beneficial, according to satisfaction surveys and interviews. The results showed that parents who participated in the ACT-based parenting program had significant improvements in several outcomes compared to parents in usual-care-only group, including reduced parenting stress, decreased depressive and anxiety symptoms, and increased confident in their parenting abilities. Their autistic children showed fewer emotional and behavioral problems after the intervention. Based on these findings, we conclude that the ACT-based parenting program is feasible and acceptable and has promising effects for parents of autistic children. In the future, larger studies should be conducted to further explore its effectiveness for different groups of parents caring for children with autism or other neurodevelopmental conditions.