The construction of hydroelectric power stations can affect the fauna, including the adaptation to the new lentic conditions, and may lead to the disappearance of some species and the colonization of others. Usually, there is a lack of information in the post-flooding phases. The present study is a preliminary qualitative survey of mammals, birds, and reptiles in the influenced area of the Balbina hydroelectric dam (01°55' S, 59°29' W). Species records were made during field trips to the reservoir with no group specific methods. The conservation status of the identified species followed the classification adopted by IUCN. Twenty-two mammals (one endangered – EN), forty-two birds and six reptiles (one vulnerable – VU) were identified. Although the list presented here is preliminary, if appropriately complemented, it can be used to understand the effects of hydroelectric dams on the Amazonian fauna.