The All Share Price Index closed at 4,215.
22, down 0.16 percent (6.82 points) while the more liquid Milanka index rose 0.02 percent (0.83 points) to close at 4,747.81.
Turnover was almost 1.4 billion rupees, according to stock exchange provisional figures.
Brokers said the market, one of Asia's best-performing this year, was hovering around record levels having risen sharply with the end of a 30-year ethnic war a year ago.
"The market opened positive today but towards mid-day there was a bit of selling pressure because of retail investor profit-taking, and ended marginally lower," said Rakshitha Perera, research manager at Bartleet Mallory Stockbrokers.
There were 65 price-gainers and 100 losers.
"It was mainly the 'mid caps' that moved today," Perera said.
"Investors are searching for stocks with low multiples.
"
With the market having reached what appeared to be a plateau, investors should "look at company fundamentals," Perera said.
"Technicals may give a wrong indication with almost everything having reached all-time high levels," he added.
"Now investors should see what growth possibilities are there and factor that into prices.
"
In Tuesday's trade, two 50,000-blocks of shares of Lanka Orix Leasing Company changed hands in an off-the-floor private deal at 255 rupees a share. The stock closed at 276.50 rupees, up 27.
Three million shares of Dialog Telekom changed hands at 8.
50 rupees each.
The share, which began moving up after the firm reported it had returned to profitability in the March 2010 quarter, closed at 8.25 rupees, down 25 cents.
Two million shares of John Keells Hotels changed hands in a deal at 20 rupees a share.
The stock closed flat at 19.75 rupees.