About 20 percent of the operator's wireline customers were now using its ADSL (asymmetric digital subscriber line) services, the telco said in a statement.
The firm said its 200,000th customers was P E D A Silva from Pulasthigama in the country's north central district of Polonnaruwa.
SLT said its network to reach rural areas in Amprai, Badulla, Puttalam, Chilaw, Hambantota, Jaffna, Kalutara, Matale, Kandy, Kurunegala, Kegalle and Ratnapura districts.
SLT said it had expanded a fibre optic cable to the island's north after the end of a 30-year war.
"Quick deployment of the Broadband infrastructure in the Northern Peninsula has provided the company with great opportunities to serve the newly opened up markets of the Northern and Eastern provinces," SLT said.
"This fibre optic cable project connects Mannar, Vavuniya, Trincomalee and Jaffna along the A9 main road (to Jaffna from central Sri Lanka).
"In addition new telephone exchanges at Mankulam and Mulathivu, located