The Garuda Indonesia plane carrying the Pope and his entourage on Friday arrived in Port Moresby, where he will stay for the next three nights.
The pontiff, departing the plane using his wheelchair, was met on the tarmac by Prime Minister James Marape and senior members of the Catholic Church in the country.
Children presented him with gifts as a military band played the anthem of the Vatican.
After the brief ceremony at the airport, Francis headed to the Vatican embassy for the evening.
His first public event in the country will be an address to political leaders on Saturday morning.
While in PNG Francis will make a day trip to the northwestern town of Vanimo, before departing the country on Monday.
He is then scheduled to visit East Timor and Singapore before returning to Rome on September 13.
Francis becomes only the second pope to visit Papua New Guinea, after St John Paul II touched down in 1984 during one of his lengthy, globetrotting voyages.
In Indonesia, the world's most populous Muslim-majority nation, Francis urged political leaders to guard against religious extremism.
The Pope also visited Istiqlal Mosque, Southeast Asia's largest, and signed a joint declaration with the national grand imam.
The statement called for "decisive action" by Catholics and Muslims to urge global leaders to confront the dangers of climate change.
The warming planet is expected to remain a focus for the Pope's visit in Papua New Guinea, where political leaders have blamed climate change for a spate of natural disasters, including a landslide in March that killed at least 2,000 people.
The Pope has stressed the importance of environmental issues throughout his 11-year papacy.
With Friday's flight, the pope will have travelled about 16,000km on the overseas trip, his longest yet.
By the time he returns to Rome, he will have clocked nearly 33,000km.
with AP
