Leo received a standing ovation as he entered the Vatican auditorium on Monday for his first meeting with representatives of the general public.
The 69-year-old Augustinian missionary, elected in a 24-hour conclave last week, called for journalists to use words for peace, to reject war and to give voice to the voiceless.
He expressed solidarity with journalists around the world who have been jailed for trying to seek and report the truth.
Drawing applause from the crowd, he asked for their release.
"The church recognises in these witnesses - I am thinking of those who report on war even at the cost of their lives - the courage of those who defend dignity, justice and the right of people to be informed, because only informed individuals can make free choices," he said.
"The suffering of these imprisoned journalists challenges the conscience of nations and the international community, calling on all of us to safeguard the precious gift of free speech and of the press."
Leo opened the meeting with a few words in English, joking that if the crowd was still awake and applauding at the end, it mattered more than the ovation that greeted him.
Turning to Italian, he thanked the journalists for their work covering the papal transition and urged them to use words of peace.
"Peace begins with each one of us: in the way we look at others, listen to others and speak about others," he said.
"In this sense, the way we communicate is of fundamental importance: we must say no to the war of words and images, we must reject the paradigm of war."
After his brief speech, in which he reflected on the power of words to do good, he greeted some of the journalists in the front rows and then shook hands with the crowd as he exited the audience hall down the central aisle.
He signed a few autographs and posed for a few selfies.
It was in the 2013 audience with journalists who covered the election of history's first Latin American pope that Pope Francis explained his choice of name, after St Francis of Assisi, and his desire for a "church which is poor and for the poor!"
During his 12-year pontificate, Francis too spoke about the value of journalism and as recently as January, he appealed for the release of imprisoned journalists during a Holy Year event with the media.
