The argument started because a stewardess on a flight between Geneva and Pristina, in Kosovo, allegedly refused to give the male passenger a sandwich, La Repubblica reported.
The passenger suffered from epilepsy, the newspaper said, and needed food to be able to take his medication.
But British newspapers reported that the man “went beserk” because he was kept “waiting too long”.
He allegedly hurled verbal abuse at the woman before punching her, knocking her to the ground. Some passengers among the 177 on board tried to intervene.
The on-board chaos prompted the pilot to make a request for an emergency landing at Rome's Fiumicino airport.
easyJet said in a statement that the “disruptive” passenger was arrested on arrival.
The stewardess suffered minor injuries, La Repubblica reported.
She was quoted by the Swiss news website, 20 Minutes, as saying: “I was totally shocked. I can't understand how anyone could react so violently over a sandwich.”
The airline added: “The safety and wellbeing of passengers and crew is always easyJet's priority.
“Whilst such incidents are rare we take them very seriously, do not tolerate abusive or threatening behaviour onboard and always push for prosecution.”
Last year, an Italian woman was arrested by police in Geneva when trying to board an easyJet flight to Venice, reportedly after a row about the size of her hand luggage.
By Anna Pujol-Mazzini