Breast feeding is the first and most important step of a healthy diet. Breast milk contains important vitamins and trace elements such as iron, zinc, copper, and vitamin A. The aim of our study was to evaluate the levels of hemoglobin, hematocrit, mean corpuscular volume, serum iron, iron binding capacity, ferritin, serum zinc, copper and vitamin A in three groups of infants, which were determined based on feeding practices. The infants in all groups were not given prophylactic iron in the first 6 mo. Two hundred fifty-nine infants were included in the study. One hundred fifty-one (58.3%) were fed with breast milk, 91 (35.1%) were fed with breast milk+formula, and 17 (6.6%) were fed with formula only. Serum copper and vitamin A levels were found to be low in formula-only fed infants compared to other groups with a statistically significant difference (p=0.017, p=0.022 respectively). The serum zinc level was found to be low in 15.9% of the breast fed infants, 17.6% of the breast milk+formula fed infants, and 23.5% of the formula-only fed infants. Although the formula-only fed infants had lower values, the difference was not statistically significant among groups (p=0.716). We think that formula fed infants potentially have low levels of copper and vitamin A in the first 6 mo and may be offered supplements. Alternatively, formula mineral and vitamin contents could be enriched. We think that further studies on this subject are needed.