During the service, the Pope was assisted by 12 people - migrants, poor or homeless people - and one of the readings was delivered by a Syrian refugee.
To mark the occasion, the Pope had lunch with around 1500 struggling people, while another 2500 were fed elsewhere.
Guests from all over Europe flocked to the Vatican City to participate in the historical event.
A chef in charge of official Vatican meals prepared the dishes, and guests enjoyed gnocchi, veal bites with vegetables and tiramisu.
“I am happy to see all these people here but we must not just help them for a day, but throughout the year,” the Pope said.
“A day like this gives a little hope, we hope for good things for the future.”