Introduction: Urinary tract infections (UTI) are common and serious clinical problems in newborn infants. Previous studies have reported that jaundice may be one of the signs of a UTI in infants. The aim of this study was to evaluate the incidence, age presentation, and severity of jaundice, sign and complications of UTI in newborns with asymptomatic, unexplained indirect hyperbilirubinemia.Methods: This was a cross sectional study conducted between May 2004 and April 2009, at the Neonatal intensive care unit, Ghaem Hospital, Mashhad, Iran. A total of 1487 infants with jaundice were recruited of which 1061 patients were evaluated for UTI. Among them, 629 infants were excluded and remaining 74 patients with UTI and 358 infants with unknown etiology of jaundice without UTI. Demographic data including prenatal, intrapartum, postnatal events and risk factors were collected by questionnaire. Biochemical markers including serum fractionated bilirubin level, urinalysis, and routine laboratory tests were measured. Written informed consent from parents of infants was obtained. The protocol was approved by the Medical Ethics Committee of Mashhad University of Medical Sciences.Results: Age presentation, age admitted to hospital, age of improved jaundice, serum bilirubin level and hospital stay in case group were significantly higher than control groups (p<0.05). UTI was diagnosed in seventy four (6.97%) cases (escherichia coli (44.4%), klebsiella pneumoniae (22%)). Pyuria and or Bacteriuria were present in 58% of patients. Renal ultrasound showed Urinary tract abnormalities in Twenty three (23%) patients. Six infants had unilateral grade 1 to 3 reflux in voiding cysto urethrogram (VCUG).Conclusion: UTI was found in 7% of asymptomatic, jaundiced infants. Therefore, we recommend that testing for a UTI be included as part of the evaluation in asymptomatic, jaundiced infants presenting after five day of life.These infants should be evaluated for Urinary tract abnormality by renal ultrasound and VCUG.