Leukocyte cell-derived chemotaxin 2 (LECT2) is a signaling molecule expressed in the liver and regulated by Wnt/β-catenin pathways implicated in hepatic metabolism. However, the clinical relevance of LECT2 in obesity and fatty liver is unknown. The objective of this study was to determine whether serum LECT2 levels are affected by of obesity and fatty liver. A cross sectional study comprising 231 Japanese adult subjects were tested for LECT2 using a highly sensitive assay. We evaluated the associations between LECT2 and the anthropometric or clinical markers of obesity and fatty liver. The mean serum LECT2 levels were 43.5 ± 13.6 ng/mL. LECT2 positively correlated with all the anthropometric measures of obesity: body mass index, waist circumference, waist-to-hip ratio, and waist-to-height ratio (W/Ht). Multiple regression analysis revealed that LECT2 is independently related to γ-glutamyl transpeptidase (γ-GTP), triglyceride, and age in males, whereas in females it was related to the homeostasis model assessment ratio, blood urea nitrogen, high-density lipoprotein cholesterol, and γ-GTP. Receiver operating characteristics curve analyses revealed that LECT2 correlated with obesity [area under the curve (AUC) 0.655, 95% confidence interval (CI) = 0.551-0.758, p = 0.002 in males; AUC 0.670, 95% CI = 0.570-0.770, p < 0.001 in females] and fatty liver (AUC 0.646, 95% CI = 0.544-0.749, p = 0.004 in males; AUC 0.733, 95% CI = 0.621-0.844, p < 0.001 in females). The present study indicates that serum LECT2 levels are increased by obesity and fatty liver, and suggests that LECT2 is a novel obesity-related protein.