Nutritional vitamin B₁₂ deficiency in infants may occur because the maternal diet contains inadequate animal products. Clinical presentations of the infants who had nutritional vitamin B₁₂ deficiency were analyzed in this study.Patients with nutritional vitamin B₁₂ deficiency were enrolled in the study between 2003 and 2010. The diagnosis was based on a nutritional history of mothers and infants, clinical findings, hematological evaluation, and low level of serum vitamin B₁₂.Thirty children aged 1 - 21 months constituted the study group. Poverty was the main cause of inadequate consumption of animal products of the mothers. All infants had predominantly breastfed. The most common symptoms were developmental delay, paleness, apathy, lethargy, anorexia, and failure to thrive. Hematological findings were megaloblastic anemia (83.3 %), thrombocytopenia (30 %), and severe anemia (13.3 %). All of the mothers had low serum B₁₂ levels; eight of them had megaloblastic anemia.The unusual clinical manifestations of vitamin B₁₂ deficiency may also be seen apart from neurological and hematological findings. Nutritional vitamin B₁₂ deficiency due to maternal deficiency might be a serious health problem in infants. Therefore, screening and supplementation of pregnant and lactating women to prevent infantile vitamin B₁₂ deficiency should be considered.