We experienced a case of herpes zoster in a 9-months aged infant as followings; The patient had no history of chickenpox or varicella vaccination. Also, her mother had no history of varicella infection and no contact history with varicella during pregnancy. The patient had only a history of exposure to chickenpox patient at 7th days after birth, but fortunately chickenpox was not developed. Sequentially, symptoms of cough with fever and tachypnea were developed on admission date(7 days had passed already after development of the initial skin lesion). On physical examination, multiple grouped painless erythematous papulovesicles with small crusts were observed on the right lower back, flank and abdomen along the T11 dermatome. Coarse breathing sound was osculated, and increased linear infiltrations on both parahilar areas were seen on chest radiography. Liver enzymes were slightly elevated. Tzanck test was negative. The initial titers of anti-VZV IgM and IgG on admission were negative, but the following titers of anti-VZV IgM and IgG were positive. The patient received treatment of acyclovir for 7 days, and healed completely without sequelae. We report this case with brief review of related literatures.