Along with the skeleton, dubbed "Balangoda man," evidence of his food items, rituals and stone tools he made were also uncovered, officials said.
"The evidence so far found has proved that the skeleton belongs to 37,000 years ago," department Director General Senarath Dissanayaka told China's state-run Xinhua News Agency.
The discoveries were made during excavation of the Fa-Hien cave, named after a Chinese Buddhist monk said to have traveled to Sri Lanka between 399 and 412 to acquire Buddhist scriptures.
The cave has yielded some of the earliest evidence of anatomically modern humans in South Asia, researchers said, and Pleistocene era human skeletal remains were first discovered at the site in 1986, confirming Homo sapiens had settled in Sri Lanka almost 40,000 years ago.
The excavation site is in Bulathsinhala, 35 miles from the capital Colombo.