The restricted and repetitive behaviors of children with autism can interfere with family functioning as well as learning and socialization opportunities for the child. To date, neither pharmacological nor comprehensive behavioral treatments have been found to be consistently effective at significantly reducing children's engagement in repetitive behaviors. We developed Family-Implemented Treatment for Behavioral Inflexibility (FITBI) to target the full variety of repetitive behaviors found in autism. For the current study, a therapist and parents of five children with autism (mean age = 48 months) co-implemented FITBI in a clinic setting over a 12-week treatment period. Using single case design methodology, significant reductions in repetitive behaviors were found for all participants and maintenance of treatment effects for 4 of 5 participants.