The main share index edged down 0.34 percent, or 19.34 points, to close at 5,730.12, after touching a near two-week high on Friday.
'At the moment, the outlook seems to be bleak,' a stockbroker said on condition of anonymity. 'We haven't seen investors buying stocks despite interest rate reduction by the central bank. There is a problem with the confidence. There could be gains, but the trend will be weak unless there is a strong market moving news,' the stockbroker said.
Brokers also said an expensive borrowing by state-owned National Savings Bank's (NSB) has also raised concern over interest rate outlook in the future.
Shares in Ceylon Tobacco Co Plc (CTC) fell 3.13 percent to 1085.00 rupees, while Sri Lanka Telecom Plc fell 4.94 percent to 38.50 rupees.
Foreign investors were net sellers of 69.1 million rupees ($522,500) worth of shares on Monday, However, they have been net buyers of 19.31 billion worth of shares so far this year.
Monday's turnover was 683.5 million rupees, less than this year's daily average of about 882 million rupees.
($1 = 132.2500 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Anand Basu)
(Reuters Messaging: firstname.lastname@example.org)(twitter.com/rangab a)