Tullow said it discovered a natural gas pay measuring about 170 feet thick in shallow waters of the Mbawa-1 exploration well off the coast of Kenya.
Angus McCoss, exploration director for Tullow, said the find was his company's first hydrocarbon discovery offshore Kenya.
"A gas discovery on prognosis in the shallowest objective at Mbawa-1 is an encouraging start to our East African transform margin exploration campaign," he said in a statement.
Tullow last month began an oil campaign in the Twiga South-1 exploration well in the country. The company has expressed confidence about the emerging energy potential for Kenya and the country could play host to an oil pipeline planned from South Sudan.
Demonstrations in Mombasa turned deadly in August following the killing of a cleric said to be an ally of al-Shabaab, an al-Qaida affiliate in control of parts of Somalia. Kenya next year holds presidential elections, the second since a deadly vote in 2007.