SLT investor relations officer Upali Mahamithawa said Chandrasena's appointment has taken effect from February 25.
Japan's NTT has a 35 percent stake in the firm but the chairman of the board is usually appointed by the government, while the chief executive is appointed by the Japanese shareholder.
Former chairman Asoka Weerasinghe de Silva has resigned from the board an official said. He was also a government nominee.
NTT is trying to sell a part of its stake to Malaysia's UT group but the issue has got in a legal tangle after a rebel lawmaker of Sri Lanka's ruling party took the matter to courts.
SLT is Sri Lanka's largest fixed access network with revenues of 43.2 billion rupees.