This study investigated the concentration of total mercury (THg) in maternal blood, cord blood, and breast milk, and its association with dietary factors. A total of 127 pregnant women in Busan, Korea were recruited. Maternal blood, cord blood, and breast milk were collected at 36 weeks of gestation, at delivery, and at one week after birth, respectively. Information about dietary habits and other factors were obtained from each subject. The mean THg concentrations in maternal blood, cord blood, and breast milk were 3.12±1.36 μg/L, 5.46±2.41 μg/L, and 0.91±2.08 μg/L, respectively. Positive correlations were found between log-transformed THg concentrations in maternal blood and cord blood (r=0.829, p＜0.001), and between maternal blood and breast milk (r=0.296, p=0.001). Multiple linear regression analysis showed that the log-transformed concentration of THg in maternal blood was positively correlated with fish consumption (β=0.345, p＜0.0001) and negatively correlated with bean consumption (β=−0.055, p=0.048). Fish consumption (β=0.482, p＜0.0001) and maternal age (β=0.025, p=0.033) were positively associated with the concentration of THg in cord blood, while negative correlations were found for bean consumption (β=−0.134, p=0.027) and parity (β=−0.172, p=0.015). Beef consumption (β=0.031, p=0.007) was positively associated with log-transformed THg concentrations in breast milk, while negative correlations were found for bean consumption (β=−0.019, p=0.003) and maternal age (β=−0.083, p=0.004). Our study found that both the dietary and demographic factors differently affected to THg concentrations among samples of maternal blood, cord blood, and breast milk.