As the Vatican press office announced on Wednesday evening, the meeting with King Charles and Queen Camilla took place in the afternoon.
Francis congratulated the royal couple on the anniversary of their wedding and returned the wishes for recovery that King Charles had sent him.
There was talk of a "special moment" on the British royal family's "X" account.
"The King and Queen were deeply touched by the Pope's kind words on their 20th wedding anniversary and were honoured to be able to convey their best wishes to him in person."
A state visit by the monarchs to the Vatican originally planned for this week had been cancelled due to the Pope's state of health following his recent release from hospital.
The private meeting, which has now materialised after all, was only confirmed at the last minute.