Behavior problems in children with autism spectrum disorders (ASD) are common and particularly stressful for parents. This study aimed to examine the feasibility of delivering a parenting program in existing services, and the feasibility of conducting a future large‐scale Randomized Controlled Trial evaluation of the effectiveness of the intervention. Parents of children aged 3–8 years with a diagnosis of ASD, or strongly suspected ASD were eligible to participate. A multicenter, pragmatic, feasibility randomized controlled trial was conducted in four specialist children's services in Wales. Families were randomly assigned to receive the Incredible Years® Autism Spectrum and Language Delays (IY‐ASLD) parent program immediately or to a wait‐list, treatment as usual control condition. IY‐ASLD sessions were delivered once a week for 12 weeks. The primary outcomes related to feasibility (recruitment, retention, fidelity, and acceptability). Preliminary outcome analyses were conducted using covariance models controlling for study site and baseline scores. From October 5 to December 19, 2016, 58 families were randomized, 29 to IY‐ASLD and 29 to control. Three parents did not attend any sessions while 19 (73%) completed the program. Fidelity of delivery was high (88%), as was satisfaction with the program. Fifty‐three (91%) completed the follow‐up measures. All 95% CIs for effect sizes included zero in exploratory outcome analyses. This study supports the feasibility of delivering the IY‐ASLD in existing services with good levels of acceptability and fidelity evident. A larger randomized controlled trial is required to examine the effectiveness of the program.