A protest is being held in solidarity with the Greeks calling for a No vote in the referendum.
Demonstrators are expected to gather outside Dublin's Central Bank from midday.
People Before Profit TD Joan Collins said that Greece needs a writedown of at least some of its latest €1.5bn debt repayment.
"If the Syriza government were to succeed in getting a debt write-down, it'll be huge egg on the face for governments in Europe," she said.
"If they want to strangle the Syriza movement, and they want them replaced by technocrats, [these are] the same people ho brought the country to its knees.
"So I think, and I hope, the people in Greece send out a clear message on Sunday.
"No matter what decision they make it's going to be very, very difficult, they're going to be facing a very, very difficult period."