Background: The Danish National Cerebral Palsy Follow-up Program (CPOP) is a nationwide program offering standardized treatment to all children with cerebral palsy (CP) since 2004. We aimed to establish if its implementation had a positive impact on the diagnostic age of CP. Methods: Children with validated CP diagnoses were identified from the Danish Cerebral Palsy Registry and the CPOP. We then compared the age at diagnosis and the clinical features of children with CP born in 2000 to 2003 with those born in 2010 to 2013. Differences in time to diagnosis were compared using log-rank test. Results: The age at diagnosis was not different in the two periods (P = 0.23), with identical overall median diagnostic ages at 13.0 months. The number of children with severe motor disability decreased markedly from 47.5% in 2000 to 2003 to 32.0% in 2010 to 2013 (P < 0.001). There was increased usage of cerebral magnetic resonance imaging; however, this was not associated with lower diagnostic age. Conclusions: The diagnostic age of CP did not change after the implementation of a nationwide follow-up program, offering standardized and early assessments. However, central clinical aspects also changed significantly between the periods compared, which possibly affected the diagnostic age.