Fiber-rich diets are associated with favorable lipid profiles, but the specific compounds and the mechanisms behind this effect are yet to be fully understood. Lignans are fiber-related polyphenols that have been associated with lower prevalence of cardiovascular disease. The objective of this study was to investigate the relationship between dietary lignan exposure, measured as the urinary concentration of their metabolites, enterolactone and enterodiol, and serum lipids in a representative sample of U.S. adults. We carried out a cross-sectional analysis of data from 1492 adults who participated in the 1999-2004 NHANES. The mean urinary concentration of enterolignans in U.S. adults was 1.9 μmol/L. The multivariate-adjusted mean differences comparing the highest and lowest enterolignan tertile were 0.06 mmol/L for HDL cholesterol and -0.17 mmol/L for TG (P < 0.05). In spline regression models, we also found an inverse association between serum TG and urinary enterolignan concentrations. Serum HDL cholesterol levels increased linearly with increasing enterolignan concentrations. Modest or no associations were found between enterolignan concentrations and serum LDL cholesterol or total cholesterol. In conclusion, enterolignan concentrations are associated with lower serum TG concentrations and greater HDL cholesterol concentrations in U.S. adults.