The discovery was made by renowned Indian biologist Sathyabhama Das Biju and a team of scientists, in the jungles of north-eastern India.
It is hoped the frogs might now be found across a wide area, from China to Thailand.
Studies of the frog have also led scientists to reclassify it as an entirely new genus.
The golf ball-sized frog lives in tree holes up to 6m (19ft) above ground, which may have helped it stay undiscovered.
Although other scientists have suggested it may have gone unnoticed simply because there are so few scientists working in the remote region.
The height at which they live is not their only quirk, with females laying their fertilized eggs in tree holes filled with water, only to return after the tadpoles hatch, to feed them with unfertilized eggs. Read more on bbc.