A historic meeting at the Vatican saw the Archbishop of Canterbury commend Pope Leo for his vocal stance against injustice.
The encounter between the two prominent religious leaders comes as both have consistently called for peace amidst ongoing global conflicts.
Separately, Dame Sarah Mullally extended an assurance of a "warm welcome" to the pontiff should he choose to visit the United Kingdom.
The Vatican summit follows recent criticism from Donald Trump, who branded the Pope "weak on crime, and terrible for foreign policy". Mr Trump demanded the pontiff "focus on being a great Pope, not a politician".
Dame Sarah has previously said she stood in solidarity with the Pope’s calls for peace.
On Monday, in her address to him after their private meeting at the Apostolic Palace – a building which includes the Pope’s private apartment and top administrative offices of the Holy See – she paid tribute to him for speaking “powerfully about the many injustices in our world today”.
She said: “Your Holiness, you have spoken powerfully about the many injustices in our world today, but you have spoken even more powerfully about hope. Your pilgrimage to Africa was full of life and joy.
“The world needed this message at this time – thank you. It reminded us that despite our sufferings, people long for life in all its fullness and countless people are working each day for this vision of the common good.”
Dame Sarah also told the Pope the King had “valued his recent visit, especially the shared prayer and spirit of fraternity it embodied”.
In October, the King and Pope Leo made history when they prayed together in a symbolic moment of unity for Anglicans and Roman Catholics across the globe.
It was the first time a British monarch, the Supreme Governor of the Church of England, had prayed at a public service with the Pope, head of the Catholic Church, since the Reformation.
The Archbishop told the Pope: “Please be assured of a warm welcome from the Church of England should you honour the United Kingdom with a visit.”
