BACKGROUND: Neonatal hyperglycemia, which is relatively common in very low birth weight (VLBW) infants, is associated with increased risk of morbidity and mortality.OBJECTIVE: To study the incidence of neonatal hyperglycemia, associated risk factors and the outcome of it in VLBW infants hospitalized in a level III NICU in Tehran.METHODS: All VLBW newborns admitted to the NICU of Mahdieh Hospital from April 2009 to March 2011 were considered eligible for this retrospective study. All relevant prenatal and perinatal data, as well as details of the hospital stay until discharge or death, were extracted from the case notes and analyzed.RESULTS: Hyperglycemia (blood suger above 150mg/dL) was observed in 179 (31.7%) of the 564 VLBW infants included in the study; 48 infants (26.8%), had received insulin. Risk factors included: low gestational age, (OR = 4.07, 95% CI = 2.09–7.93, P < 0.001), extremely low birth weight (ELBW) , (OR = 5.97, 95% CI = 3.77–9.44, P < 0.001), dopamine administration (OR = 2.19, 95% CI = 1.32–3.65, P = 0.003), intralipid (OR = 1.52, 95% CI = 1.04–2.22, P = 0.03), Low APGAR score at 5 minutes (OR = 4.44, 95% CI = 2.48–7.94, P < 0.001), RDS and its complications (OR = 4.20, 95% CI = 2.55–6.93, P < 0.001), were independently associated with hyperglycemia. Other findings with hyperglycemia were: high incidence of IVH >grade II (OR = 2.88, 95% CI = 1.28–6.49, P = 0.01), hospital stay more than 28 days in survivors,(OR = 3.56, 95% CI = 2.02–6.25, P < 0.001), mortality (OR = 4.42, 95% CI = 3.00–6.52, P < 0.001) and more retinopathy of prematurity (ROP ≥ stage II) in survivors (OR = 2.05, 95% CI = 1.11–3.78, P = 0.02).CONCLUSION: Neonatal hyperglycemia developed in approximately one-third of our VLBW neonates. Relative prevalence and associated findings underscore the need for preventive measures and prompt management.