The vast majority of children with cerebral palsy (CP) are surviving into adulthood due to improved surgical and health care practice. Thus, the expiration of paediatric services means that a new population of adults with CP has emerged that must transition into an ill-equipped adultoriented system. Informed by the perspective of complexity theory, this case study used both quantitative and qualitative data to examine the primary healthcare transition of youth with CP living in Sault Ste. Marie, Ontario. Analysis of Ontario Health Insurance Program claims showed service use changes due to both the expiration of paediatric services and the changing health needs of individuals with CP as they age. Physicians commented on challenges due to the complexity of the CP disease process and the benefits of shared care and teamwork in discussing transition. Future research and clinical practice designed to address transition barriers need to be informed by complexity theory.