Valeriy Tolmashev, who appeared very agitated, tried to hijack the Alitalia flight around 1930 GMT.
The flight arrived in Rome's Fiumicino airport at 2005 GMT and the apparently unbalanced man was handed over to police, ANSA said, citing Italian border police. All the passengers were safe.
Tolmashev approached the hostess and held a small knife or nail file against her neck, according to different witnesses.
He said he wanted to hijack the plane, with 131 passengers on board, to the Libyan capital.
The 48-year-old was quickly overpowered by four stewards and passengers who wrestled him to the floor before frogmarching him back to his seat. A doctor on board administered a sedative to the would-be hijacker.
Informed sources were quoted as saying the man, whose motives were not known, was an adviser to Kazakhstan's delegation at UNESCO, the UN educational, scientific and cultural organization, in Paris.
He had not reserved a hotel in Rome and could not give an address where he was to stay in the Italian capital.
Checks were under way with the French police.
Tolmashev, who had no police record or known links with international terrorism, according to the Italian inquiry team, was under border police custody at the airport.
A group of passengers was to be questioned to help the inquiry. But the cabin staff's intervention was so quick and effective at the front of the plane that passengers at the back did not notice anything.
The hostess, traumatized and slightly bruised in the neck, was treated at the airport. Her condition was not giving rise to concern, Alitalia officials said.