The organisation, which recently accepted political responsibility for the murder of a left-wing rapper, are the third largest party in the country.
The rally, held in historic Syntagma Square, was literally painted red with SYRIZA flags and shirts, albeit not as many as January's final rally or the 'No' rally prior to July's referendum.
For the third time in eight months, people are preparing to head to the polling stations.
Tension and disappointment dominated the Greek parliament as it prepared to vote on a set of austerity measures so tough, they'd have Thatcher dancing in her grave.
I går demonstrerede grækere mod den nye redningsplan ved at sætte ild til Syriza-flag.
Paul Mason's foreword from The Global Minotaur: America, Europe and the Future of the Global Economy by Yanis Varoufakis, Greece's ex-finance minister who resigned this morning.
Many preferred the idea of austerity and budget cuts to the fear of the unknown.
"A 'no' vote gives us an opportunity to build bonds and relations with other people and fight for something different to what we have been going through for the last five years."
The country filed for bankruptcy before it was even a sovereign state.
Some will be voting 'Yes' to more austerity and being part of Europe, some will be voting 'No' and then there are those who will be going on holiday.
If Syriza achieve their aims, they could end up changing things far beyond Greece.
We asked four people living on the outskirts of society if they believe that Greece's new left-wing government can show them better days.