The Zoological Society of London (ZSL) and the KWS set up camera traps in the north-eastern forest after Grace Wambui of the ZSL caught a sighting of the elusive animal.
"This is an important discovery," ZSL senior field conservation biologist, Rajan Amin, said. "We will continue our work to document the forest's rich biodiversity and to determine if this is a new species of elephant-shrew."
The mammal, which is named because of its long, flexible trunk-like nose, could add to the 17 species of elephant-shrew known to science, all of which are endemic to Africa.
Also known as sengis, the animals are descended from creatures that evolved in Africa over 100 million years ago. They share a common ancestor with elephants and sea cows.
"With their ancient and often misunderstood ancestry, their monogamous mating strategies, and their charismatic flexible snouts, they are captivating animals," said Galen Rathbun from the California Academy of Sciences.
The KWS believes the sighting shows the importance of protecting threatened habitats.
"This discovery has underlined the conservation significance of these isolated forests," said Sam Andanje from the KWS.
"Unfortunately, they are highly threatened by on-going rapid coastal development and there is now an urgent need for an effective management plan."
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