"We all have a responsibility to act so that the world may be a community of brothers who respect each other, who accept their diversity and who take care of one another," the pope said on Catholic World Peace Day.
The first pope from Latin America said violence and injustice "cannot leave us indifferent or immobile" and said 2014 should bring "a real commitment to build a society with more justice and more solidarity".
"We have to stop on this road of violence! What is happening in the heart of man? In the heart of humanity? We have to stop!" the pope said.
Francis said he hoped that a "cry for peace" in the world would encourage dialogue and "tear down walls that prevent enemies from seeing each other as brothers".
The pope also made an unscheduled visit to the church of Santa Maria Maggiore in Rome later on Wednesday, where he prayed in front of a famous icon of the Virgin Mary.
It was the same church that he visited on the first morning after his election on March 13, 2013.
At a New Year mass in St Peter's Basilica earlier on Wednesday, Francis prayed in his homily for people "who hunger and thirst for justice and peace" in the world.
He also called on the faithful to show "strength, courage and hope" in the year to come, speaking in his homily in front of thousands of people in the church.
Francis, formerly the Archbishop of Buenos Aires Jorge Mario Bergoglio, was elected following his predecessor Benedict XVI's momentous resignation in February 2013 -- a first for the Catholic Church since the Middle Ages.
His down-to-earth style and commitment to reforming the Vatican have raised hopes in the Roman Catholic Church following years of turmoil due to shocking child sex abuse scandals and growing secularisation in the West.
The 77-year-old Francis has called for the Church to reach out more to the vulnerable and has said it should be a "poor Church for the poor" that is less "Vatican-centric" and gives more power to local bishops.