Around 1,000 people thronged a narrow passageway outside the Church of Saint Anna, his local parish church just inside the Vatican gates, as he arrived for mass.
In dramatic contrast with the reserved style of his predecessors, he walked along a hastily constructed barrier reaching deep into the crowd, shaking hands, laughing and joking.
It is the first time he has had a chance to meet members of the public up close since being elected on Wednesday.
There were chants of "Francesco, Francesco" as he turned and walked through the iron gates out onto the main street, where most of the crowd were waiting, leaving his anxious security men rushing to keep up.
When two clerics were brought up and introduced to him, attempting to drop to their knees, he hurriedly ushered them back onto their feet.