Salome Zurabishvili, the leader of the opposition and a former foreign minister, said that Saakashvili's agreement to meet his political adversaries signalled a success for government opponents.
"In the end he saw reality ... and realised that silence and ignorance is no longer possible. This is a first success," she told about 3,000 protesters who had gathered outside parliament.
"This is a sign for us that we have been on the right track during the last 30 days," she said.
Zurabishvili will be joined at the talks with Levan Gachechiladze, a former presidential candidate, Irakli Alasania, a former envoy to the United Nations, and Kakha Shartava, the leader of the National Forum party.
Saakashvili's announcement comes a day after about 20,000 opposition loyalists demonstrated in Tbilisi, the capital, to mark one month since protests against the president began.
The opposition called for direct talks with Saakashvili on Friday, during a meeting with David Bakradze, the parliament speaker.
Clashes at an anti-government protest last week and a brief military mutiny have led to concerns that there unrest could spread through the rest of Georgia.
The country is hosting military exercises by Nato, the Western military alliance, which has provoked fierce criticism from neighbouring Russia.
Vladimir Putin, Russia's prime minister, said on Sunday that the Nato exercises were a tacit sign of Western support for Saakashvili's government.
"Against this background they [Nato] decided to carry out the war games," Putin said in an interview with Japanese media.
"Of course, this cannot be seen as anything other than support for the ruling regime. And why support such a regime?"
Moscow has in recent months expressed its opposition to what it calls Nato's expansion into Georgia and Ukraine, two former Soviet republics whose governments have expressed their desire to have stronger ties with the West.
But since Saakashvili came to power after a popular 2003 revolution, he has been criticised by many Georgians for his increasingly autocratic rule and for last year's military defeat to Russia over control of the breakaway region of South Ossetia.