The park covers 30,821 hectares (119.00 sq mi) of land area and was established on 30 June 1972. Before the designation of the national park, the area was used for shifting cultivation (chena farming). The farmers were gradually removed once the national park was declared.

The habitat surrounding the reservoir includes marshes, the Walawe River and its tributaries, forests and grasslands. Dead tree standing in the reservoir are visual reminders of the extent of forest cover before dam construction. Areas of open grassland are abundant as a result of former chena farming. The Teak plantation beyond the southern boundary, below the dam was planted before the declaration of the park.

Udawalawe has a reputation for harboring large stocks of Asian Elephants. Many elephants are attracted to the park because of the Udawalawe reservoir. As many as 350 animals are believed to be permanently resident.

Also the Department of wildlife conservation’s orphaned Elephant rehabilitation centre founded in 1995, aptly named Udawalawe Elephant Transit Home is situated bordering the park at a different location the purpose of looking after abandoned elephant calves within the park. At the centre baby elephants are bottle fed at given times.

Apart from Elephants, Chital or Spotted Deer, Wild Boar and Feral buffaloes are a common sight but Golden Jackal, Toque Macaque,Tufted Grey Langur and Indian Hare are also regularly encountererd. Occasionally if lucky one would to come upon Jungle cats or even Leopard.

As far as the birds are concerned the park consists of some interesting raptors. Crested Hawk Eagle, Crested Serpent Eagle, Black-shouldered Kite, Shikra, White-bellied Sea Eagle and Grey-headed Fish-eagle are regularly seen. Montague’s Harrier, Pallid Harrier, Booted Eagle, Shaheen Falcon a race of the peregrine are also recorded.