At the eighth round of balloting among more than 1000 parliamentarians and regional delegates in the Chamber of Deputies, loud applause broke out when Mattarella passed the 505 votes needed for election.
Mattarella, 80, had ruled out remaining in office but with the country's political stability at risk he changed his mind in the face of appeals from parliamentary leaders who met him at his palace earlier in the day.
In Italy's political system, the president is a powerful figure who gets to appoint prime ministers and is often called on to resolve political crises in the euro zone's third-largest economy, where governments survive around a year on average.
"I had other plans but if needed, I am at your disposition," parliamentarians quoted the snowy-haired Mattarella as telling them after they went cap-in-hand to his official Quirinale residence to ask him to remain in office.
A former constitutional judge and one-time centrist lawmaker, Mattarella was initially elected president in 2015, becoming the first head of state from the island of Sicily.
Little known to many Italians, Mattarella had a reputation for being introverted and austere but he quickly won over his compatriots with his quiet, unassuming manner and calm handling of repeated political crises and the COVID-19 health emergency.
On the eve of the parliamentary ballot to find his successor, polls showed that most Italians wanted him to stay.
Mattarella appeared destined for a life as a law professor but plunged into politics after his brother Piersanti, the-then governor of Sicily, was shot by the Mafia in 1980.
A photograph showed Mattarella holding him shortly before he died.
Joining the Christian Democrat party that his father had helped found, Mattarella was elected to parliament in 1983 and served, among other things, as education minister, defence minister and deputy prime minister over the next two decades.
