The aims of this study were to evaluate zinc, copper, and iron concentrations in the transitory milk of Korean lactating mothers and to investigate the relationship between these concentrations and maternal diet. Human milk samples were collected between 5 and 15 days postpartum from 96 healthy, lactating mothers in postpartum care centers in Seoul, Korea. Dietary intake during lactation was determined based on a 3-day dietary record. The mean zinc, copper, and iron concentrations in the human milk samples collected were 3.88 ± 1.74 mg/L, 0.69 ± 0.25 mg/L, and 5.85 ± 8.53 mg/L, respectively. The mothers who consumed alcoholic beverages during pregnancy had tended to have lower concentrations of zinc and copper, as well as significantly lower concentrations of iron, in their milk (p < 0.047). In contrast, the mothers who took daily supplements had much higher iron concentrations in their milk (p = 0.002). Dietary intakes of zinc, copper, and iron during lactation did not affect the concentrations of zinc, copper, and iron in the milk samples analyzed. Intakes of vitamin C, selenium, and iodine were associated with the concentration of copper in the milk samples analyzed, and consumption of food categorized as 'meat and meat products' was positively associated with the concentration of zinc. Consumption of rice was the top contributor to the concentrations of all three minerals. In conclusion, associations between maternal diet and nutrient concentrations in transitory human milk can provide useful information, particularly in regard to infant growth.