Pope Francis told journalists and officials on Saturday that the world is seeing a scaling back of democracy, Anadolu Agency reported.
"We cannot avoid noting with concern how today, and not only in Europe, we are witnessing a retreat from democracy," said Francis at his welcoming ceremony at the Greek Presidential mansion.
The pontiff said the migration issue is a "horrendous modern Odyssey," aiming to draw attention to the refugee crisis in Europe.
"Europe continues to hesitate, and the EU has often fallen prey to forms of nationalistic self-interest, rather than being an engine of solidarity, and has appeared at times blocked and uncoordinated," he said.
The pope said democracy is complex but wider participation is needed and warned against the attractive easy answers of populism, adding that democracy would be the answer to authoritarianism.
Greek President Kateina Sakellaropoulou welcomed the pontiff and praised him for his social sensitivity and his support.
"I welcome you with special honour and emotion," she said, adding that Francis' visit has a symbolic value as it shows his concern in the wider region.
Quoting several Greek philosophers, Francis pleaded for the return of the common good in politics and to be wary of politicians with "an obsessive quest for popularity, and unrealistic promises."
He was welcomed by Sakellaropoulou who extended an invitation and was greeted at the airport by Foreign Affairs Minister Nikos Dendias, Vatican ambassador and leaders of the Greek Catholic Church.
The pope is also expected to visit Lesvos island and its reception centres for a second time since 2016.