The present study, a qualitative case series report with a quantitative component, explores the relation between changes in family interaction patterns and therapy outcome at 9-month follow-up in a child-and familyoriented psychosocial treatment program developed to treat pediatric primary headache. Changes in the family interaction patterns of 38 children and adolescents diagnosed according to International Headache Society criteria were examined via qualitative methods. Therapy outcome was assessed on an 11-point numeric rating scale measuring the reduction of subjectively experienced global headache burden. At follow-up, 1 subgroup of families showed positive change, and a 2nd subgroup displayed either unchanged or worsened headache-associated interaction patterns. Participants from families with a positive change in headache-associated interaction patterns showed a 64% reduction (p ϭ .00) of global headache burden; participants with unchanged or worsened family interaction patterns showed only a 17% reduction. The findings are illustrated by case histories and discussed in the context of dynamic systems theory.