The 84-year-old pope had part of his colon removed in an operation on 4 July – the first time he has faced a significant health concern during his eight-year papacy.
He returned to the Vatican on Wednesday, where he needed help from assistants to get out of his car.
Hundreds of people were gathered in the sunny square and cheered when he appeared at the open window this morning.
As is often the case, at the end of his address the pope mentioned some of the events dominating world headlines.
He urged an end to the recent public unrest in South Africa and called for peace and dialogue in Cuba after unprecedented, protests rocked the Communist-run country.
“I am also close to the dear people of Cuba in these difficult times, in particular to the families who especially suffer,” Pope Francis said to cheers.
He also referred to catastrophic floods in recent days in Germany, Belgium and the Netherlands, which have killed more than 180 people.