Objective To investigate the significance of urinary NGAL in assessing tubulointerstitial lesions in IgA nephropathy. Methods Urine NGAL level was detected by ELISA in 115 cases with IgAN, 30 cases with non-IgAN glomerulonephritis, and 30 healthy controls. Results The levels of urine NGAL in IgAN or non-IgAN glomerulonephritis patients were higher than that in healthy controls (P<0.01). The levels of urine NGAL in IgAN were significantly correlated with many clinical and pathology parameters. The independent influencing factors on urine NGAL included blood albumin, urine protein, NAG enzyme, urine osmotic pressure, and tubulointerstitial lesions. To evaluate whether or not TIL existed, ROC analysis of urine NGAL combining NAG enzyme showed that AUC was 0.850, and the sensitivity and specificity were 83.3% and 73.3% respectively, while the AUC for serum creatinine was 0.675. Conclusion The levels of urine NGAL in IgAN could reflect the degree of illness. The combined detections of urine NGAL and NAG enzyme are better in evaluating whether or not TIL existed than the single detection of serum creatinine, urine NGAL, urine NAG, or osmotic pressure alone.