BACKGROUND: Few trials have been conducted to address the psychological difficulties of parents in managing their child's asthma. Fostering parental psychological flexibility through Acceptance and Commitment Therapy (ACT) may help parents to accept these psychological difficulties and improve their management of childhood asthma. METHODS: In this randomized controlled trial, a 4-session, group-based ACT plus asthma education (ACT group) was compared with an asthma education talk plus 3 telephone followups (control group) to train parents of children diagnosed with asthma. The use of health care services due to asthma exacerbations in children and the psychological well-being of their parents were assessed before, immediately after, and at 6 months after the intervention. RESULTS: A total of 168 parents and their children aged 3 to 12 years with asthma were consecutively recruited in a public hospital in Hong Kong. When compared with the control group, children whose parents were in the ACT group made significantly fewer emergency department visits (adjusted 6-month incidence rate ratio = 0.20; confidence interval [CI] 0.08 to 0.53; P = .001) due to asthma exacerbations at 6 months postintervention. These parents also reported a decrease in psychological inflexibility (mean difference = 25.45; CI 27.71