The frail pontiff insisted on keeping up his regular busy schedule but set aside time for a birthday lunch and cake with his closest aides.
The occasion also was marked by publication of his latest book, which mixes memories from his native Poland, a touch of self-criticism and a defense of priestly celibacy.
"It will be a regular working day and above all a thanks to God for the gift of life," said Vatican spokesman Joaquin-Navarro Valls. He reported that the Vatican had been flooded with birthday greetings for John Paul.
John Paul, who marked 25 years in the papacy in October and has since become the third-longest serving pope in history, is pushing ahead despite Parkinson's disease and hip and knee ailments. He plans a two-day trip to Switzerland early next month, his first foreign travel since a pilgrimage to Slovakia in September.
On Tuesday, he received visiting American bishops and Prime Minister Jose Durao Barroso of Portugal, whose delegation broke into "Happy Birthday" in Portuguese. The pope was clearly pleased, smiling and raising his right hand to bless the group.
In the evening, John Paul was meeting with the president of Poland.
"To the ever-young custodian of peace," said the Vatican newspaper L'Osservatore Romano in its birthday greeting.
In bookstores in Italy and elsewhere, John Paul's latest literary work "Get Up, Let Us Go" went on sale. It is a sequel to "Gift and Mystery," an account of the pontiff's early priesthood that was released in 1996.
It came out a decade after publication of the heavily autobiographical "Crossing the Threshold of Hope," which sold 20 million copies around the world.
The latest book draws on the pope's years in Krakow, where - as Karol Wojtyla - he served as bishop and then archbishop, but also touches on his years since his election as the first Polish pope in 1978.
He recalls his passion for the theater and being told he would have been a "great actor" but said the suffering around him from World War II led him to abandon a career on the stage.
The pope said that those contesting celibacy have raised the issued of the loneliness for priests, but that he personally never felt lonely.
In a moment of self-criticism, the pope notes that "a part of a pastor's role is to admonish" and says that maybe he failed to be strict enough during his time in Krakow.
The pope wrote the book in March-August 2003, writing some parts himself in Polish and dictating others.
"This is not a memoir of times past, but a record of belief and faith," Polish Cardinal Franciszek Macharski said at the book launch in Krakow. "There are also glimpses of love for the country and for the people."
Italian publisher Mondadori says it is still negotiating the rights for the English-language edition. The royalties from it will go into a special fund for charitable use, Navarro-Valls said.
By Victor L. Simpson