Objective The objective of the meta-analysis is to integrate results on the achievement of developmental milestones in emerging and young adults with chronic pediatric physical illness. Methods Through electronic databases and cross-referencing, 165 comparative studies were identified. Random-effects meta-analysis was computed. Results Emerging and young adults with chronic pediatric illness had lower rates of finishing advanced education, finding employment, leaving the parental home, marrying, and becoming parents than healthy peers; between-group differences ranged from 22 to 38%. They also had lower income levels than healthy peers. Stronger differences were found for respondents with neurological illnesses and sensory impairment than in individuals with other chronic diseases. Lower success rates were also observed if the illness/disability is highly visible to others and in the case of longer illness duration. Conclusions Interventions are recommended aimed at preventing and reducing lower rates of mastering the adult milestones of individuals with pediatric chronic illness.