However, analysts said investors were cautious and awaited the outcome of a loan deal with the International Monetary Fund.
The benchmark stock index ended up 0.13 percent at 6,442.53, its highest close since Jan. 14.
"It looks like new phase of wind blowing through the market. The negativity is fading away and buying is coming in slowly," said Reshan Kurukulasuriya, Chief Operating Officer at Richard Pieris Securities Pvt Ltd.
The central bank kept benchmark rates steady on Tuesday, as expected, as it gauges the effect of the recent tightening amid final stages of talks with the IMF for a $1.5-billion loan to tide over a payments crisis.
Yields on short-term government securities were also steady at a weekly auction on Wednesday.
The measures also signalled market interest rates may not rise as early as the market expected.
Turnover stood at 560.1 million rupees, less than this year's daily average of around 767.8 million rupees.
Foreign investors were net buyers of 15.5 million rupees ($106,382.98) worth of equities on Thursday, but have been net sellers of 2.97 billion rupees worth of shares so far this year.
Shares in Ceylon Tobacco Company Plc rose 0.91 percent while Ceylon Cold Stores Plc rose 2.85 percent. ($1 = 145.7000 Sri Lankan rupees)