Aims: The use of corticosteroids and abandoning the delivery are of preventive actions of newborns' respiratory distress syndrome. The aim of this clinical trial was to compare the effect of one versus two doses of Betamethasone on the outcomes of preterm infants. Materials & Methods: In this quasi-experimental clinical trial, 100 preterm labor pregnant women who referred to Sanandaj Be'sat Hospital in 2013 were selected by purposive sampling method and were divided into one dose (12mg Betamethasone) and two doses (12mg Betamethasone with the interval of 24 hours) groups. Information about delivery and gender, weight and Apgar scores of newborn were recorded in the checklist. Newborns were examined for infant respiratory distress syndrome, necrotizing enterocolitis, cerebral hemorrhage and neonatal death. Data were analyzed in SPSS 20 software by Chi-square and Mann-Whitney U tests. Findings: 14 newborns (28%) in one dose and 13 (24.5%) in two doses group had respiratory distress syndrome (p=0.689). 4 newborns (8%) in one dose and 7 (13.2%) in two doses group had enterocolitis and 8 newborns (16%) in one dose and 9 (17%) in two doses group needed respiratory support (p>0.05). Conclusion: Single-dose or two doses administration of Betamethasone in preterm mothers have no impact on newborn after birth.