Methemoglobinemia is not a rare condition arising from the exposure to hemoglobin-oxidizing agents such as nitrates-nitrites present in well water or vegetables. Infants < 3 months of age are more susceptible than adults because of lower amounts of a key enzyme, NADH-cytochrome b5 reductase, which converts methemoglobin back to hemoglobin. We report 2 infants, aged respectively 2 and 1 months, suffering from methemoglobinemia, fed with a formula that was reconstituted with a high concentration of courgette soup to resolve constipation. They developed a severe cyanosis with methemoglobinemia (respectively 30.4 and 27%) and were hospitalized and treated with methylene blue at 1%. After 12 h the syndrome was completely resolved. Home-prepared infant foods containing vegetables are potential causes of methemoglobinemia. It is important not to feed infants with vegetables having a high nitrate content (e.g., courgette, spinach, beets and green beans) to resolve constipation since, particularly in the first months of life, they may cause severe methemoglobinemia.