Scientists from Universiti Malaysia Sarawak (UNIMAS) found three of the missing long-legged Borneo rainbow toads up a tree during a night time search.
The team had spent months scouring remote mountain forests for the species.
Prior to these images, only illustrations of the toad had existed.
These were drawn from specimens that were collected by European explorers in the 1920s.
Conservation International, which launched its Global Search for Lost Amphibians in 2010, had listed the toad as one of the “world’s top 10 most wanted frogs”.
Dr Indraneil Das led a team that searched the ridges of the Gunung Penrissen range of Western Sarawak, a boundary between Malaysia’s Sarawak State and Indonesia’s Kalimantan Barat Province.
After several months of night-long expeditions, one of Dr Das’s graduate students eventually spotted a small toad in the high branches of a tree.
“Thrilling discoveries like this beautiful toad, and the critical importance of amphibians to healthy ecosystems, are what fuel us to keep searching for lost species,” said Dr Das.
“They remind us that nature still holds precious secrets that we are still uncovering.”
Dr Robin Moore of Conservation International, who launched the Global Search for Lost Amphibians, was delighted by the discovery.
He said: “To see the first pictures of a species that has been lost for almost 90 years defies belief.
“It is good to know that nature can surprise us when we are close to giving up hope, especially amidst our planet’s escalating extinction crisis.
“Amphibians are at the forefront of this tragedy, so I hope that these unique species serve as flagships for conservation, inspiring pride and hope by Malaysians and people everywhere.”