OBJECTIVE: Shared decision making (SDM) between service users and providers is increasingly being suggested as a key component of good healthcare. The aim of this research was to explore whether child- and parent-reported experience of SDM was associated with child- and parent-reported improvement in psychosocial difficulties and clinician-reported functioning at the end of treatment in child and adolescent mental health services (CAMHS). METHOD: The sample comprised N = 177 children (62% female; 31% aged 6-12 and 69% aged 13-18) with a variety of mental health problems from 17 services where routinely collected data consisted of presenting problems at outset, child- and parent-reported change in symptoms between Time 1 and Time 2 (Strengths and Difficulties Questionnaire; SDQ), clinician-reported change in functioning between Time 1 and Time 2 (Children’s Global Assessment Scale; CGAS), and experience of SDM at Time 2 (as measured by responses to the Experience of Service Questionnaire; ESQ). RESULTS: Analysis revealed that both child- and parent-reported experience of SDM were associated with higher levels of child- and parent-reported improvement in psychosocial difficulties. However, child-reported experience of SDM was only associated with higher levels of child-reported improvement when their parents also reported higher levels of SDM. CONCLUSION: In CAMHS, involving both children and parents in decision making may contribute to enhanced treatment outcomes.