Wearing her habit and a crucifix around her neck, Sister Cristina immediately thanked God for her victory in The Voice of Italy and recited an "Our Father" prayer to puzzlement among the organisers.
"I want Jesus to come in here!" said the wholesome 25-year-old with a self-effacing manner, who was dressed in the sensible black shoes and ankle-length black skirt she has worn throughout.
"My presence here is not up to me, it's thanks to the man upstairs!" said Sister Cristina after winning out against a 28-year-old long-haired hard rocker who had just performed "Stairway to Heaven".
Watch her sing Beautiful That Way, a song from the Oscar-winning La Vita è Bella (Life is Beautiful) in last night's final:
Sister Cristina, a reformed rebel from Sicily who now lives with her order in Milan, has won a record contract with Universal although she has hinted she does not want a musical career.
"I'm not here to start a career but because I want to impart a message," said the soul sister, adding that she was following Pope Francis's calls for a Catholic Church that is closer to ordinary people.
She shot to fame in recent months in this predominantly Catholic country with her versions of songs like "Girls Just Want To Have Fun" and "Time of My Life" from the film "Dirty Dancing".
It was a performance of Alicia Keys's "No One" that first drew attention in March and she sang it again on Friday to cheers from an audience that included nuns from her Ursuline Order.
There was some confusion when one panel judge — rock star Pier Pelu – joked she was the "devil incarnate", prompting the host to quickly step in saying this was intended with "maximum irony".
The talent show was also apparently being followed in the Vatican corridors of power, with top culture official Cardinal Gianfranco Ravasi tweeting a quote from a Roman thinker: "If we commit injustice, God will leave us without music."
Sister Cristina has already sung alongside Kylie Minogue and Ricky Martin and Keys defined as "pure energy" Suor Cristina's performance, which received more than 50 million YouTube hits.
She has also received an endorsement from actress Whoopi Goldberg – the star of the 1990s comedy "Sister Act" where she is a singer playing a nun.
But Sister Cristina still defined herself as a "humble servant" and ascribed her sudden success to a "thirst for joy" among television viewers.
"Since Pope Francis talks of a bible of joy I think I'm on the right track," she said on Wednesday in the run-up to the showdown.
'Mysterious and special force'
Fame has brought media scrutiny to her past, including interviews with an ex-boyfriend and with Claudia Koll, the director of the musical academy where she trained – herself an ex-starlet who is now a lay sister.
"Cristina's personal journey has brought her to maturity and artistic fullness thanks to a mysterious and special force. By giving herself to the Lord, she has enriched her art," Koll said in a recent interview.
Sister Cristina has said she used to rebel against religion when she sang in a band but was inspired to be a nun when she auditioned for a part in a musical about the founder of the Ursuline Order, Saint Angela Merici.
She became a novice in 2009 and worked for two years with poor children in Brazil before formally joining the order and still has to take her final vows.
She may have won audience hearts but her popularity is not universal, even in Italy and critics have ascribed her success more to novelty value than to genuine talent.
Singer Emma Marrone, who represented Italy in this year's Eurovision song contest, said the sensation surrounding the nun was "an insult to showbusiness".
Sister Cristina herself has hinted she might prefer a return to a "normal life" with her community in Milan, singing "with young people in church and in schools".
"I will continue to sing wherever the Lord wants," she said.