The aim of this study was to demonstrate that neutrophil gelatinase-associated lipocalin (NGAL) increased before the onset of microalbuminuria in patients with type 1 diabetes mellitus (T1DM), representing an important biochemical parameter with high sensitivity and specificity to make a precocious diagnosis of "normoalbuminuric" diabetic nephropathy (DN). Serum NGAL (sNGAL) and urinary NGAL (uNGAL) levels were evaluated in a cohort of fifty patients affected by T1DM. They had no signs of clinical nephropathy. Thirty-five healthy subjects (HS) were recruited. sNGAL levels were significantly higher compared with those measured in HS [193.7 (103.2-405.4) vs. 46.4 (39.8-56.2) ng/ml; p < 0.0001], as were uNGAL levels [25.5 (14.2-40.2) vs. 6.5 (2.9-8.5) ng/ml; p < 0.0001]. sNGAL was found to be directly correlated with glycated hemoglobin. uNGAL also positively correlated with albuminuria, whereas an inverse correlation was found with uric acid. After multivariate analysis, significance was maintained for the correlation between uNGAL and microalbuminuria. In ROC analysis, sNGAL showed a good diagnostic profile such as uNGAL. NGAL increases in patients with T1DM, even before diagnosis of microalbuminuria representing an early biomarker of "normoalbuminuric" DN with a good sensitivity and specificity. NGAL measurement could be useful for the evaluation of early renal involvement in the course of diabetes.