Background: Children born very preterm are at risk for cognitive deficits and motor impairment. Enhanced protein intake immediately after very preterm birth has been associated with favorable growth and improved neurodevelopment. It is unknown whether increased protein intake after discharge from the hospital affects long-term neurodevelopment. Objective: The primary objective was to assess neurodevelopment from infancy to 8 years in preterm-born children who received either protein-enriched formula (PDF), standard term formula (TF), or human milk (HM) after discharge. The secondary objective was to assess the correlation between outcomes obtained at 24 months corrected age (CA) and at 8 years. Methods: This RCT included 152 children born very preterm (gestational age ≤32 weeks) and/or with a very low birth weight (≤1500 g) of whom 102 were randomly assigned to receive PDF (n = 54) or TF (n = 48) from term age to 6 months CA. A control group of infants fed HM (n = 50) was also included. Neurodevelopmental outcomes were assessed at 24 months CA (cognitive and motor functioning; n = 123) and at 8 years (estimated Full Scale Intelligence Quotient, visual-motor skills, verbal memory, attention, and motor functioning; n = 76). Results: The PDF and TF groups were not significantly different in neurodevelopmental outcomes. The HM group had a better cognitive score compared with the PDF group: at 24 months CA 92.9 ± 12.5 vs. 105.2 ± 18.6, P < 0.001 and at 8 years 98.1 ± 11.3 vs. 105.8 ± 9.1, P = 0.017 (P = 0.002 and P = 0.080, respectively, after adjustment for parental educational level). Correlations between outcomes at 24 months CA and 8 years were weak: r = 0.35 and r = 0.37 for cognitive and motor outcomes, respectively. Conclusions: PDF did not improve long-term neurodevelopmental outcomes as compared with TF. However, these results should be interpreted with caution considering the substantial attrition at follow-up. Furthermore, the correlation between outcomes at different ages was weak, emphasizing the need for long-term follow-up of nutritional intervention studies in preterm-born children.