To investigate perinatal factors and early morbidities associated with early serum phosphate (sPhos) levels in a cohort of preterm infants. Retrospective data were obtained from the medical records of a cohort of 454 infants born at < 32 weeks gestational age. Serum phosphate levels were directly associated with gestational age, body weight z-score, and Apgar scores and inversely associated with timing of enteral nutrition initiation and diet consisting of mostly breast milk. Maternal hypertension, lactate levels, early symptomatic hypotension, and total protein supplemented on days 1 to 3 were also inversely associated with sPhos. Morbidities that were found to be associated with sPhos did not persist after adjustment for confounding factors.Conclusions: We report a novel association between early sPhos and timing and content of enteral nutrition, as well as with the early neonatal hemodynamic condition of preterm infants. This information may help identify infants at risk for low sPhos and aid in the nutritional strategy utilized in these patients. This study did not identify early morbidities associated with sPhos.What is Known:• High initial amino acid intake is associated with increased risk of Refeeding like syndrome and hypophosphatemia, among preterm infants.What is New:• Early enteral nutrition, starting within the first 72 h of life, is associated with higher serum phosphate (sPhos) compared to nothing per os (NPO).• sPhos was not associated with early adverse neonatal outcomes.