Metabolized by liver sinusoidal endothelial cells, autotaxin (ATX) is a secreted enzyme considered to be associated with liver damage. We sought to clarify the diagnostic ability of ATX for liver fibrosis in 593 biopsy-confirmed hepatitis C virus (HCV)-infected patients. The diagnostic accuracy of ATX was compared with clinical parameters and the established fibrosis biomarkers Wisteria floribunda agglutinin-positive Mac-2-binding protein, FIB-4 index, AST-to-platelet ratio, and Forn's index. Median ATX levels were consistently higher in female controls and patients than in their male counterparts (P < 0.01). Serum ATX concentration increased significantly according to liver fibrosis stage in overall and both genders (P < 0.001). The cutoff values of ATX for prediction of fibrosis stages ≥F1, ≥F2, ≥F3, and F4 were 0.8, 1.1, 1.3, and 1.7 mg/L, respectively, in male patients and 0.9, 1.7, 1.8, and 2.0 mg/L, respectively, in female patients. The area under the receiver operating characteristic curve for ATX to diagnose fibrosis of ≥F2 (0.861) in male patients was superior to those of FIB-4 index and Forn's index (P < 0.001), while that in female patients (0.801) was comparable with those of the other markers. ATX therefore represents a novel non-invasive biomarker for liver fibrosis in HCV-infected patients.