However, apparent low public awareness risks rendering the votes invalid if turnout is not high enough.
Campaigners for the change in the citizenship law say it will help second-generation Italians born in the country to non-European Union parents better integrate into a culture they already see as theirs.
The referendum risks failure if at least 50 per cent plus one of eligible voters don't turn out.
Voting began on Sunday and continues for two days.
Data from Italy's Interior Ministry showed that national turnout so far stood at 15.9 per cent almost half of the 30.3 per cent registered at the same time of the day in the latest comparable referendum held in 2011.
A yes vote would reduce the residency requirement from 10 to five years before citizenship is granted.
The new rules, if passed, could affect about 2.5 million foreign nationals who still struggle to be recognised as citizens.
Supporters say this reform would bring Italy's citizenship law in line with many other European countries, promoting greater social integration for long-term residents.
It would also allow faster access to civil and political rights, such as the right to vote, eligibility for public employment and freedom of movement within the EU.
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