The two men then posed for photograghs and the pope kept a stern face while Trump beamed for the cameras.
We do not know what these two men said to each other during their private meeting.
What do you think of the Trump ladies' Vatican outfits?
Through a translator, the Pope asked the First Lady: "What do you give him to eat-potica?"
On her visit to Saudi Arabia, Melania wore a conservative black jumpsuit with full sleeves, however, she did not cover her head.
After the meeting, they exchanged gifts. He gave the Pope a boxed set of five first-edition books by murdered U.S. civil rights leader Martin Luther King and a bronze sculpture.
Dunne, of the Carnegie Endowment for International Peace, said that "while they are likely to differ again in the future, today's meeting poured balm on a wounded relationship".
"If you look at her style, it's still very much her and her style of dress but being sensitive to the place and host nation for sure", Stephanie Grisham said.
"We went to the Pope", Trump told Tusk and Juncker.
As Mr Trump and the pope said goodbye at the door of the study, Mr Trump told him: "Thank you, thank you".
British Prime Minister Theresa May visited Saudi Arabia last month sans head scarf as well.
"All eyes were on the Vatican on Wednesday when Trump, along with members of his family and political inner circle, shared a private audience with the pontiff". "It was an honor to be with the pope". Francis also differs sharply with Trump on the need to combat climate change and economic inequality.
Their encounter was smooth and brief, lasting about 30 minutes. But the timing Wednesday was tight as Francis had his weekly Wednesday general audience.
Ivanka and Jared were a constant presence at Trump's side in Israel.
Mr Trump and the Pope were famously at loggerheads previous year, when the former said building a wall - the one proposed between the United States and Mexico - would show Mr Trump was "not a Christian".
"(Jackie) and the Pope spoke French to each other, and the Pope, who was anxious about how to address her, said, "Ah, Jacqueline!" when they met", Andersen Brower said. The pontiff has been a vocal advocate for aiding refugees, particularly those fleeing the violence in Syria, deeming it both a "moral imperative" and "Christian duty" to help. To which Trump hit back, remarking it was "disgraceful" of the Catholic Church leader to question his faith.
President Trump's wife and daughter took a leaf out of former First Lady Michelle Obama's book for their meeting.