"Today I received a summons to appear from the Rome prosecutor's office," she said on her Facebook page, adding that she was "very calm," and had "total confidence in the justice system".
According to the Agi news agency, Raggi is to be questioned next week about allegations of abuse of power and fraud as part of the probe into Raffaele Marra, Rome City Hall's personnel head.
Last month Raggi's populist Five Star Movement (M5S) party, led by comedian Beppe Grillo, stripped Raggi of the power to make "important decisions" after Marra's arrest.
Marra, seen as part of Raggi's inner circle, is suspected of accepting an illegal payment from a real estate developer in 2013 while he was head of housing policy under former Rome mayor Gianni Alemanno.
Raggi defended Marra when she was elected last year, calling him indispensable. But in December she admitted having "made a mistake" in trusting him.
But she also approved the hiring of his brother, Renato Marra, as head of tourism for the city. It is about this appointment that she will be questioned by prosecutors, Raggi said.
M5S prides itself on being scrupulously ethical and having no links to what it sees as the sleazy ways of Italian politics.
READ ALSO: What is Italy's Five Star Movement?
The Movement's leader, Beppe Grillo. Photo: Giuseppe Cacace/AFP
Last month its leader Grillo said the party must "change gears," adding "we must fix the errors and leave no room for doubt".
"Mistakes were made, and Virginia Raggi has admitted them. She trusted the least trustworthy people in the world," he added on his blog on December 17th.
Grillo had warned Raggi the day before that "important decisions, like nominations" should now be endorsed by party leadership.