The pontiff has sent a letter to Australian prime minister, Tony Abbott, who is leading the G20 summit in Brisbane.
"Throughout the world, the G20 countries included, there are far too many women and men suffering from severe malnutrition, a rise in the number of the unemployed, an extremely high percentage of young people without work and an increase in social exclusion which can lead to criminal activity and even the recruitment of terrorists," Francis said.
David Cameron will join Barack Obama and other major world leaders at the meeting which Australia says will focus on growing global economic growth.
The country has so far resisted pressure to put climate change higher on the agenda.
But Pope Francis urged them to reconsider: "In addition, there are constant assaults on the natural environment, the result of unbridled consumerism, and this will have serious consequences for the world economy.
"It is my hope that a substantial and productive consensus can be achieved regarding the agenda items. I likewise hope that the assessment of the results of this consensus will not be restricted to global indices but will take into account as well real improvements in the living conditions of poorer families and the reduction of all forms of unacceptable inequality.
"I express these hopes in light of the post-2015 development agenda to be approved by the current session of the United Nations assembly, which ought to include the vital issues of decent work for all and climate change."
The Holy Father also urged leaders to discuss the persecution of Christians in Iraq and Syria by militant group ISIS.
He spoke of the "the terrible backdrop of military conflicts" and urged "an ever broader agreement which can lead, through the United Nations legal system, to a definitive halt to the unjust aggression directed at different religious and ethnic groups, including minorities, in the Middle East".
He added: "It should also lead to eliminating the root causes of terrorism, which has reached proportions hitherto unimaginable; these include poverty, underdevelopment and exclusion.
"It has become more and more evident that the solution to this grave problem cannot be a purely military one, but must also focus on those who in one way or another encourage terrorist groups through political support, the illegal oil trade or the provision of arms and technology. There is also a need for education and a heightened awareness that religion may not be exploited as a means of justifying violence."
He finished the letter by offering prayers for all the leaders.