The 47-year-old woman had fled Sicily after being convicted of fraud by a court there in 2017 and sentenced to two years in prison, police said on Wednesday.
After heading for the north of Italy, she hid out in various convents in the Lombardy and Piedmont regions, claiming to be a nun with health problems.
But she was caught out last week when a nun at a convent in Gallarate, north of Milan, became suspicious about her identity, local media reported.
The nun reportedly told police that the woman’s stories “were full of contradictions” and she often changed her version of events.
The sister called police, who discovered the fugitive was carrying stolen ID and took her to the police station, where they identified her as being wanted in Sicily.
She was arrested again and now faces fresh charges of claiming false identity in addition to her previous conviction.
The unnamed woman, originally from Acqui Terme near Alessandria, had repeatedly changed her identity as she moved from convent to convent, police said.
Fugitives in the overwhelmingly Catholic country have a long history of using religious disguises to dodge justice.
In 2013, a Calabrian man dressed as a priest was arrested while trying to cross the French-Italian border with six kilograms of cocaine in his luggage.
And the notorious former head of the Sicilian mafia Totò Riina reportedly used to wear a priest's cassock when meeting other members of the organisation.