<b><i>Aim:</i></b> To study the effect of catch-up growth in the 1st year on cognition, health-related quality of life (HRQoL), problem behavior and growth in young adults. <b><i>Methods:</i></b> We included individuals without severe complications and born small for gestational age (SGA; n = 228 for weight, n = 203 for length) or with a low head circumference (HC, n = 178) or a low weight adjusted for length (n = 64) in the Collaborative Project on Preterm and SGA Infants. Neonatal growth was standardized (standard deviation scores for gestational age, SDS_GA) according to GA-specific reference charts. Catch-up growth was defined as SDS_GA at 1 year of age adjusted for SDS_GA at birth. Cognition was defined by the Multicultural Capacity Test-Intermediate Level, HRQoL by the London Handicap Scale (LHS) and the Health Utility Index Mark 3 categorized into 4 levels (Multi-Attribute Utility, MAU), and problem behavior by the Young Adult Self-Report. We adjusted for potential confounders. <b><i>Results:</i></b> Most adults were born preterm (93.7%). A higher catch-up growth in the 1st year was associated with better cognition (B = 2.57, 95% CI 0.08-5.05 for weight), less disabilities according to the LHS (B = 2.06, 95% CI 0.35-3.78 for HC) and the MAU (OR = 0.67, 95% CI 0.48-0.95 for HC) and higher final height (B = 0.33, 95% CI 0.18-0.47 for weight; B = 0.41, 95% 0.28-0.55 for length, and B = 0.18, 95% CI 0.04-0.33 for HC) in young adulthood. <b><i>Conclusion:</i></b> There are long-term benefits of catch-up growth.