To explore the associations between nutrition in the first 28 days after birth with somatic growth from birth to term-equivalent age, brain volumes at term-equivalent age, and neurodevelopment at 24 months of corrected age.Prospective cohort study of 149 infants born from 2011 to 2014 at <30 weeks of gestation in a tertiary neonatal nursery in Australia. The following data were collected: average daily energy, protein, fat, and carbohydrate intakes from birth until 28 days, and the difference in weight and head circumference z scores between birth and term-equivalent. Total brain tissue volumes were calculated from brain magnetic resonance imaging at term-equivalent age. Children were assessed at 2 years of corrected age with the Bayley Scales of Infant and Toddler Development-Third Edition. Relationships of nutritional variables with growth, brain volumes, and cognitive, language, and motor development were explored using linear regression.Complete nutritional data were available for 116 (78%) of the cohort. A 1 g/kg/day higher mean protein intake was associated with a mean increase in weight z score per week of 0.05 (95% CI 0.05, 0.10; P = .04). There was a lack of evidence for associations of any nutritional variables with head circumference growth, with brain volumes at term-equivalent age, or with 2-year neurodevelopment.Only higher protein intakes in the first 28 days after birth were associated with better weight growth between birth and term-equivalent age in very preterm infants. Nutrition in the first 28 days was otherwise not substantially related to brain size or to neurodevelopmental outcomes.