Purpose : The aim of this study was to evaluate the diagnostic accuracy of urinary biomarkers such as neutrophil gelatinase-associated lipocalin (uNGAL) and β-2 microglobulin (uB2MG) in early detection of UTI in infants younger than 3 months with fever. Methods : A total of 422 infants aged 3 months (male:female=267:155; mean age=56.4days), who were admitted for fever, were retrospectively included in this study. We compared uNGAL and uB2MG between the UTI and non-UTI groups at the time of admission. The sensitivity, specificity, accuracy, and area under the curve (AUC) of uNGAL and uB2MG for diagnosing UTI were assessed. Results : Among 422 patients, 102 (24.2%) patients were diagnosed with UTI. Levels of uNGAL were higher in the UTI group than non-UTI group (366.6 vs. 26.9, p 0.001). Levels of uB2MG were not different between the two groups. Multivariate analysis revealed that uNGAL was an independent predictive factor of UTI (p0.001). The sensitivity, specificity, and accuracy were 90.2%, 92.5%, and 91.9% for uNGAL, and 48.0%, 43.8%, and 44.8% for uB2MG, respectively. AUC of uNGAL was 0.942 and that of uB2MG was 0.407. Conclusions : Accuracy of uNGAL in the diagnosis of UTI is high in febrile infants aged 3 months. uNGAL can help in the early diagnosis and treatment of UTI in infants.