In a video published online, the Italian head of state is seen greeting the Queen upon arrival at Buckingham Palace.
The president is momentarily silent as the Queen attempts to make small-talk, before an interpreter rushes to his aid.
“Is this the first time you have been to London?” the interpreter translates. The president responds that he has been to the city several times, before responding to her next question about how long he has been president.
The two heads of state then had a private 45-minute meeting followed by a tour of the Italian art collection at Buckingham Palace.
Mattarella, who has been Italian president since February, later met with the UK’s Foreign Secretary Philip Hammond for 30 minutes at the Italian embassy in London, Corriere Quotidiano reported.
The pair spoke about Syria, Libya and immigration, in a meeting described as “very frank and friendly”.
The president also gave a speech at the London School of Economics (LSE) about Europe, where he expressed his confidence that the UK would choose to stay within the EU in the upcoming referendum and urged for a united and integrated Europe.
"It is a friendly country that wants to stay in the European Union, and we hope to stay together," he was quoted by Ansa as saying.
On Friday Mattarella was expected to pay a visit to the House of Lords, the second chamber of UK parliament, before returning to Italy.