This paper describes development and validation of the Parental Psychological Flexibility (PPF) Questionnaire, a parent-report measure designed to assess psychological flexibility among parents of pre-adolescents and adolescents (aged 10–18 years). Psychological flexibility within parenting refers to parents’ accepting negative thoughts, emotions and urges about one’s child and still acting in ways that are consistent with effective parenting. Exploratory factor analysis (n = 178 parents) of a 43-item draft measure, resulted in a 30-item, 3-factor structure. Three subscales were created, consistent with the psychological flexibility literature: acceptance, cognitive defusion and committed action. A second sample of parents (n = 192) was then used to confirm the factor structure and reliability and validity of the PPF. Results supported the 3-factor structure, reduced the number of items to 19 and demonstrated that the PPF subscales have adequate reliability and validity and are thus suitable for researching psychological flexibility among parents of pre-adolescents and adolescents.