Echinococcus oligarthrus hydatid cyst disease was diagnosed in two imported wild-caught Brazilian agouti (Dasyprocta leporina). The cysts were found incidentally during routine examinations and never appeared to cause any apparent clinical signs. Identification of the cysts was confirmed via histopathology. Over a period of 2 yr, the cysts calcified but did not reabsorb. Treatment with praziquantal and albendazole did not appear to affect the cysts. Agoutis are intermediate hosts of E. oligarthrus in the wild, where jaguars (Panthera onca) and pumas (Puma concolor) act as definitive hosts. Caution is advised when working with E. oligarthrus–infected animals because of the zoonotic disease potential.