The purpose of this study was to investigate the protective effects against porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) in suckling piglets by oral administration of IgY. Twenty piglets were divided into two groups with the same number: group I (treated with IgY) and group II (not treated). Group I was administerd orally with IgY for three days from one-day-old and experimentally challenged with PEDV and TGEV at four-day-old. The other was administered with saline solution and challenged with PEDV and TGEV at four-day-old. Serum antibody titers against PEDV and TGEV were examined by enzyme-linked immunosorbent assay (ELISA) and the detection of PEDV or TGEV antigen from feces and small intestines was performed by reverse transcription-polymerase chain reaction (RT-PCR) and indirect immunofluorescence (IFA). The antibody titers of the group I was higher than that of the other, and lasted at the end of experiment. In the detection tests of both virus from feces and small intestine, the rate of the group I was lower. Based on these results, oral administration of IgY may be effective to prevent the diarrhea caused by PEDV and TGEV.