The central bank, before the market opened, kept the key policy rates steady after it unexpectedly cut them by 50 basis points month ago.
"For the market to continuously move up, there should be some news. Even keeping the rates steady does not help investors to get in," said a stockbroker who declined to be named.
The main stock index fell 1.02 percent, or 64.95 points, to 6,307.43, the lowest close since May 16.
However, foreign investors were net buyers of shares for a 21st straight session. The bourse saw a net foreign inflow of 291.6 million rupees ($2.31 million), extending the year-to-date inflows to 15.6 billion rupees.
Foreign investors accounted for around 46.47 percent of the day's turnover of 883.7 million rupees, less than this year's daily average of 1.04 billion rupees.
Shares in conglomerate John Keells Holdings fell 3.00 percent to 265.00 rupees, while leading mobile phone operator Dialog Axiata Plc lost 3.23 percent to 9.00 rupees.
The rupee ended weaker at 126.45/50 per dollar from Thursday's close of 126.30/40 on demand for greenbacks from importers, dealers said.
($1 = 126.4250 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Jijo Jacob)