Pope Benedict XVI is attending Mass in Angola's capital Luanda, on the last stop of his week-long African tour.
The pontiff, who arrived in Angola on Friday from Cameroon, will later meet youths at a city football stadium.
On Friday, he made a powerful attack on corruption, which analysts say is rife in oil-rich Angola.
The climax of the visit will be on Sunday, when two million people are expected to hear the Pope address an outdoor service.
The 81-year-old said in a televised address in Luanda on Friday that Africans could transform their continent with integrity, magnanimity and compassion.
Thousands of people welcomed the Pope at Luanda's airport, the BBC's Louise Redvers says.
The Pope said in his address that Africans needed "a firm determination to change hearts and finally put a stop, once and for all, to corruption".
Benedict's speech was echoed by President Jose Eduardo dos Santos, who has been Angola's leader for the past three decades and through a civil war which has left hundreds of thousands dead.
Mr dos Santos' party won elections last year that critics said were marred by fraud and corruption.
Angola, a former Portuguese colony, is rich in diamonds and oil, but war has left most of its people in poverty.
The Pope sparked controversy earlier on his tour for remarks refusing to advocate condoms as a way to help stop HIV/Aids, prompting France, Holland and even the pontiff's native Germany to express concern.