The All Share Price Index closed at 4,248.37, up 4.83 points, while the more liquid Milanka index fell 0.09 percent (4.13 points) to close at 4,788.58.
Turnover was 1.3 billion rupees, according to stock exchange provisional figures.
"There was selling pressure due to investors realizing gains," Rakshitha Perera, research manager at Bartleet Mallory Stockbrokers said.
"Investors are looking for stocks with growth potential.
"
Brokers said retail participation was lower due to floods caused by heavy rain disrupting vehicular traffic in Colombo.
There was high interest in banking sector shares, brokers said.
Commercial Bank closed at 249.00 rupees, up 25 cents with over 683,000 shares changing hands in a privately negotiated off-the-floor deal, and Hatton National Bank closed at 244.25 rupees, up 3.00 rupees with 895,000 shares privately traded between 242 to 245 rupees, brokers said.
Nations Trust Bank closed at 37.25 rupees, down 25 cents, Sampath Bank closed at 285.00 rupees, up 1.75 and Seylan Bank closed at 54.
50 rupees, down 50 cents.
Sri Lankan Telecom closed flat at 37.
50 rupees, and Dialog Telekom, a unit of Axiata Malaysia also closed flat at 8.50 rupees.
Investors took profits from selected midcap and high value stocks, brokers said.
At the end of trade there were 48 gainers versus 103 losers, brokers said.
"We could expect the volatility to continue as investors search for stocks with growth potential," Perera said.
Aitken Spence closed at 1,550.75 rupees, up 75 cents, Hayleys closed at 285.00 rupees, down 1.50, Hemas Holdings closed at 140.25 rupees, down 1.75 and John Keells Holdings closed at 180.
50 rupees, down 75 cents.
Abans Electricals closed at 184.00 rupees, down 2.00, Asia Capital closed at 34.75 rupees, down 1.25, Capital Reach Leasing closed at 22.00 rupees, down 1.00, First Capital Holdings closed at 19.
50 rupees, down 1.25 and Lanka Milk Foods closed at 97.
50 rupees, down 1.50.