Blastocystis hominis is a common intestinal parasite observed in fecal examination. On the other hand, the transmission of this parasite is certainly unknown. The transmission of B. hominis can be realized by animal contact and the contamination by water and food with excreted cysts from the reservoir hosts. B. hominis isolated from 25 humans, their pets, and tap water was identified by polymerase chain reaction using sequenced tag site primers in this study. B. hominis isolates obtained from humans and pets were identified as subtype1, subtype2, and subtype3 while B. hominis isolates obtained from tap water were also identified as subtype1. The B. hominis isolates obtained from humans in this study were defined as the same as the subtypes of the B. hominis isolates obtained from the pets, of which these people keep at their homes, and the tap water. These findings reveal that the source of B. hominis infection could be pets and tap water.