“Let us stop ignoring reality, stop constantly shifting responsibility, stop passing off the issue of migration to others," Pope Francis said during a visit to the Greek island.
The Moria camp on the island of Lesbos is way over capacity, forcing people to live in squalor.
Self-harm and suicide attempts are common, doctors said.
For many people, the island is the first glimpse of Europe after crossing the Aegean Sea.
Tourism is way down on Lesbos thanks to imagery of people swarming the island.
The Huffington Post joined an EU rescue mission off the coast of Lesbos, Greece.
"I was most scared of seeing my children die right in front of me," one woman said.
The pontiff wants to "show a sense of solidarity and responsibility" on the front line of the migrant crisis.