However, sympathizers of the Kurdish cause weren't the only ones to criticize the Turkish president's visit.
Returning a visit made by the pope to Turkey in 2014, Erdogan spoke privately with Francis for about 50 minutes in the pontiff's frescoed study in the Vatican's Apostolic Palace, which he uses mostly for ceremonial purposes.
Armenia and the Armenian lobby claim that Turkey's predecessor, the Ottoman Empire allegedly carried out "genocide" against the Armenians living in Anatolia in 1915.
They also discussed the situation in the Middle East, giving special attention "to the status of Jerusalem".
The two leaders were expected to discuss their shared opposition to Donald Trump's recognition of Jerusalem as the Israeli capital. The Turkish government said the US-backed Syrian Kurdish militia there is a terrorist organisation and an extension of Kurdish insurgents fighting within Turkey.
Finally, the statement said they discussed "the situation in the Middle East, with particular reference to the status of Jerusalem, highlighting the need to promote peace and stability in the region through dialogue and negotiation, with respect for human rights and global law".
Following the private meeting the Pope gifted the President a bronze medallion, which shows an angel over the northern and southern hemispheres while a dragon tries to attack, Radio Free Europe said.
Kurdish protestors tried to enter St. Peter's Square on Sunday to protest the pope's meeting with Erdoğan but were blocked by police.
"I don't speak to people who support terrorism".
In Italy, the Turkish president will also meet his counterpart, Sergio Mattarella, and Prime Minister Paolo Gentiloni.