The main index closed up 0.22 percent, or 13.01 points, at 5,829.05.
Foreign investors were net buyers of 36.6 million rupees of shares on Thursday, extending the year-to-date net foreign inflow to 22.5 billion rupees worth.
Shares in Nestle Lanka rose 1.19 percent to 1,973.30 rupees in low volume trading, while conglomerate John Keells Holdings fell 0.10 percent to 208.40 rupees.
Stockbrokers said investors were worried about September-quarter earnings. Many listed firms are expected to release their quarterly earnings this month.
The day's turnover was at 525.7 million rupees ($4.01 million), less than this year's daily average of 860.9 million rupees.
($1 = 131.1000 Sri Lanka rupees)
(Reporting by Ranga Sirilal and Shihar Aneez; Editing by Subhranshu Sahu)
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