"We are all children of one heavenly father, we belong to the same human family and we share a common destiny," Francis said, speaking from a window overlooking a packed St Peter's Square.
"This brings a responsibility for each to work so that the world becomes a community of brothers who respect each other, accept each other in one's diversity, and takes care of one another," he said.
Setting aside his prepared text for a moment, he expressed impatience with violence in the world. "What is happening in the heart of man? What is happening in the heart of humanity" to cause such violence? Francis asked. "It's time to stop."
He hoped "the gospel of brotherhood speak to every conscience and knock down the walls that impede enemies from recognising that they are brothers."
The Catholic church dedicates January 1 to the promotion of world peace.
In his homily at Mass in St Peter's Basilica, Francis spoke of humanity's journey in the year unfolding and invoked what he said were "words of blessing," explaining that they are "strength, courage and hope".
"Not an illusory hope," he added, "based on frail human promises, or a naive hope which presumes that the future will be better simply because it is the future."