Francis, celebrating Mass in St Peter's Basilica, said people wonder how it's possible that "the arrogance of the powerful continues to demean the weak, relegating them to the most squalid outskirts of our world."
He highlights the men, women and children risking their lives to flee war, hunger and persecution.
He is urging people to overcome indifference and "leave behind the false neutrality which prevents sharing."
Francis' formula for peace centers on cooperating to build "an ever more just and fraternal world."