Anthony Albanese spoke to Pope Leo XIV about his mother after being ushered into St Peter's Basilica in Rome following the Catholic leader's inauguration mass.
"I spoke to him about my mother who would be, I'm sure, looking down from Heaven with the biggest smile she's every had," the prime minister told reporters at the Vatican on Sunday.
The conversation took place after a number of world leaders were taken into the basilica to greet the Pope after the mass.
Mr Albanese, who was raised Catholic in a housing commission flat in Sydney, often references his single-parent mother and her influence on his life.
Mr Albanese also met with other world leaders on the sidelines of the historic event at the Vatican, including Canadian Prime Minister Mark Carney, European Union President Ursula von der Leyen and Ukrainian President Volodymyr Zelenskiy.
Ms von der Leyen reportedly raised the prospect of closer security ties between the EU and Australia, similar to other arrangements between the trading bloc and Japan and South Korea.
Mr Albanese was reportedly cautious but indicated he was open to considering the proposal, which might involve future military exercises and other co-operation in areas of mutual interest, according to the ABC.
Australia has been pursuing a free-trade agreement with the EU, which is yet to be settled.
Federal frontbencher Tanya Plibersek agreed there had been a few "sticking points".
"There's about a thousand names that the European Union wants to restrict the use of, and they are parmesan, fetta, prosecco, a whole lot of names of food that are related to the place where they come from," she told Seven's Sunrise program.
"But we would say that the parmesan made in Australia is world's best and we want to make sure that any free-trade agreement with the European Union is a clear advantage for Australia.
"We'll continue to work through it."
A trade agreement with the EU would open up a market for Australian goods and services to more than 400 million people.
As a bloc, the EU was Australia's third largest two-way trading partner in 2022/2023. It's also the sixth largest export destination and the third largest services export market.
Two-way trade is valued at around $110 billion.