The main share index ended 0.22 percent, or 13.54 points, lower at 6,015.20.
Top mobile phone operator Dialog Axiata fell 1.14 percent to 8.70 rupees, while Sri Lanka Telecom, the No. 1 fixed-line phone operator, ended 1.27 percent weaker at 39 rupees.
The index hit a near 10-week low on Tuesday on concerns over the rupee's weakening trend and possible foreign outflows.
The local currency was steady on Monday as the deputy central bank governor said he expected the pressure on the rupee to ease as fund inflows pick up after a sell-off in June.
Turnover on Monday was 441 million rupees ($3.37 million), well below this year's daily average of about 972 million rupees.
($1 = 130.8500 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Subhranshu Sahu)