Vatican television has shown footage of Pope John Paul II murmuring a few words at a Mass in hospital.
The Pope is expected to give the traditional Easter blessing
It was the first time the pontiff's voice had been heard since 24 February, when he underwent throat surgery to help ease his breathing difficulties.
The Pope uttered a barely audible blessing at the end of a service attended by two Tanzanian bishops.
The Pope is expected to return to the Vatican for the start of Easter holy week on Palm Sunday, on 20 March.
He is planning to give his traditional Easter blessing on Easter Sunday, the Vatican said, while a number of cardinals have been chosen to preside over other traditional Easter ceremonies.
In the footage shown on Friday, the Pope, dressed in a purple vestment, reportedly attended mass with the two visiting cardinals seated in an armchair.
He could barely be heard reciting a prayer, but in a separate meeting he reportedly told the prelates, "God bless you", in a much clearer and stronger voice.
The Pope's spokesman, Joaquin Navarro-Valls, said doctors have yet to decide whether and when a pipe inserted into his throat to help him breathe can be removed.
The 84-year-old pontiff suffers from Parkinson's disease and other ailments.
He was readmitted to the hospital just two weeks after he was treated there for flu-like symptoms.
The Vatican said the Pope's health continued to improve and that he had been responding well to speech and breathing therapy.
Since his operation, the Pope has not attempted to speak to the faithful, but he has been uttering a few words to selected visitors allowed to see him at the hospital.
He also has appeared at his hospital window three times to wave at pilgrims.