The diagnosis of biliary atresia (BA) remains a clinical challenge because affected infants have signs, symptoms, and serum liver biochemistry that are also seen in those with other causes of neonatal cholestasis (non-BA). However, an early diagnosis and prompt surgical treatment are required to improve clinical outcome. Recently, the relative abundance of serum matrix metalloproteinase-7 (MMP-7) was suggested to have discriminatory features for infants with BA. To test the hypothesis that elevated serum concentration of MMP-7 is highly diagnostic for BA, we determined the normal serum concentration of MMP-7 in healthy control infants, and then in 135 consecutive infants being evaluated for cholestasis. The median concentration for MMP-7 was 2.86 ng/mL (interquartile range, IQR: 1.32-5.32) in normal controls, 11.47 ng/mL (IQR: 8.54-24.55) for non-BA, and 121.1 ng/mL (IQR: 85.42-224.4) for BA (P < 0.0001). The area under the curve of MMP-7 for the diagnosis of BA was 0.9900 with a cutoff value of 52.85 ng/mL; the diagnostic sensitivity and specificity were 98.67% and 95.00%, respectively, with a negative predictive value of 98.28%. Conclusion: Serum MMP-7 assay has high sensitivity and specificity to differentiate BA from other neonatal cholestasis, and may be a reliable biomarker for BA.