A mouse species, which was thought to have been extinct in New South Wales for 150 years, has been found living in a drought-ravaged national park in the state's far west.

It is the first time anyone has seen the desert mouse in the Sturt National Park near Tibooburra since 1857.

The manager of the area's National Parks and Wildlife Service, Ingrid Witte, says a PhD student at the University of New South Wales, Ulrike Kloecker, made the important discovery.

"We certainly didn't expect any new finds," she said.

"[Ms Kloecker] has been out their travelling and had to get the manual book out again to identify this species because she had never come across it and yep, there it was."

Ms Witte says further investigations will now take place to try to find other desert mice.

She says it is exciting that the park can still yield mammals despite the prolonged drought.

"Although it is a rodent, it doesn't look like a little house mouse that we know of. This one is really a beautiful colour," she said.

"It has a buff-orange ring around its eyes, it is quite an attractive little thing."

Ms Ulrike, who works in Sturt National Park investigating the ecology of the small mammal and reptile communities, said in a statement that she was excited by the discovery.