Background: Blood transfusion is common in infants. Due to the weakened immune system of newborns and the risk of blood transfusion complications, it is necessary to pay more attention following or after to blood transfusion. The aim of this study was to evaluate the frequency and risk factors of blood transfusions in hospitalized neonates. Methods: A cross-sectional study was performed on 1106 infants admitted in the neonatal intensive care unit (NICU) of Mustafa Khomeini University Hospital, Tehran, Iran, from spring 2009 to 2012. Frequency and the reason for of blood components transfusion including fresh frozen plasma, platelets, whole blood, packed red blood cells, cryoprecipitate and relationship with gestational age, sex, birth weight, Apgar score, duration of hospitalization, use of mechanical ventilation were assessed. Statistical analysis was performed with SPSS statistical software, version 16 (IBM, Armonk, NY, USA) and statistical test, chi-square test, independent t-test and analysis of variance (ANOVA). Results: Among 1106 infants admitted to the neonatal intensive care unit, 221 infants (%19.98) received blood products. 82 of all (37%) were female and 139 (%63) were female. 113 (51%) of neonate were preterm and 108 (48%) were term. From 361 times of blood transfusions, 121 infant (54.75%) received at least one blood product. The frequency of blood transfusion was between 39 and 1 times, with an average of 3.65 times per infant. Frequency of fresh frozen plasma infusion was 173 (47.9%), packed cell 122 (33%), platelet 32 (8.8%), cryoprecipitate 20 (5.1%) and whole blood 3 unit (0.83%). The most common causes for fresh frozen plasma transfusion was replacement therapy 140 (80%), for packed cell, to correct symptomatic anemia 68 (55.6%), for platelet transfusions was to prevent bleeding in  neonates with thrombocytopenia 20 (62.5%) and cryoprecipitate for bleeding caused by DIC in 18 infant (90%). There was significant relation between frequency of blood transfusions with gestational age (P=0.002), birth weight (P=0.01), cause of hospitalization (P=0.001) using of ventilator (P=0.002), and length of hospital stay (P=0.001). Conclusion: With attention to the guidelines of blood transfusions and controlling factors affecting premature birth and low weight infants, reducing length of hospital stay and duration of mechanical ventilation, frequency and complications of blood transfusion can be effectively decreased.