"Thirty-seven heads of government have confirmed participation, which is more than at (the last Commonwealth Summit in) Perth," Information Minister Keheliya Rambukwella told reporters.
The Commonwealth Heads of Government Meeting will be held here during November 15-17.
Indian Prime Minister Manmohan Singh's participation is uncertain.
However, rights groups have expressed concerns about the summit being held in Sri Lanka due the country's human rights record.
Only Canadian Prime Minister Stephen Harper has said that he would boycott the summit because of Sri Lanka's failure to show progress on rights.