Pope Francis arrives on the stage to preside over the celebration of the Palm Sunday mass on April 2, 2023 at St. Peter s square in The Vatican. AFP
The 86-year-old's admittance to hospital on Wednesday with breathing difficulties sparked concerns he may not be well enough to attend a series of rites in the most important week in the Christian calendar.
But Francis had promised to be present, and he waved briefly to some 30,000 people as he rode in his popemobile through the square, which was adorned with over 35,000 plants and flowers.
He looked serious as he followed the procession through St Peter's Square of religious figures, including red-robed cardinals, carrying large palm leaves and olive branches.
Palm Sunday marks the arrival of Jesus in Jerusalem before his crucifixion. Easter Sunday, which this year is on April 9, celebrates his resurrection from the dead.
As a smiling Francis had left Rome's Gemelli hospital Saturday after a three-night stay, he quipped to well-wishers who asked how he was "I am still alive!"
The head of the world's 1.3 billion Catholics has suffered from increasing health issues over the past few years, including knee problems which have forced him to use a wheelchair and walking stick.
Francis was expected to remain seated throughout the mass, while a cardinal conducts the ceremony at the altar.
The Vatican said this was an arrangement adopted prior to the pope's latest illness, as he is no longer able to stand for long periods.
Francis felt unwell Wednesday following a general audience in St Peter's Square, but his condition improved after he was given antibiotics.
The hospitalisation was his second since 2021, when he underwent colon surgery, also at Gemelli.
His increasing health issues over the past year have sparked widespread concern, including speculation that he might choose to retire rather than stay in the job for life.
Francis marked 10 years as the head of the worldwide Catholic Church earlier this month.
He has pushed through major governance reforms and sought to forge a more open, compassionate Church, although he has faced internal opposition, particularly from conservatives.
He has repeatedly said he would consider stepping down were his health to fail him -- but said last month that, for now, he has no plans to quit.
Francis' previous stay at Gemelli in July 2021 lasted 10 days. He was admitted after suffering from a type of diverticulitis, an inflammation of pockets that develop in the lining of the intestine, that required surgery.
In an interview in January, the pope said the diverticulitis had returned.