The New York Times Thursday quoted sources briefed on the raids as saying "charges against roughly two-thirds of the defendants were lodged" in Brooklyn federal court.
The alleged crimes involved "classic mob hits" and "senseless murders," the attorney general said.
"In one instance, a victim allegedly was shot and killed during a botched robbery attempt and two other murder victims allegedly were shot dead in a public bar, because of a dispute over a spilled drink," he said, in an apparent reference to a 1980s shooting in an Irish bar in the New York City borough of Queens.
Holder went on to explain the alleged criminal activities of organized crime affect various economic sectors.
As an example, he said there were alleged schemes to steal money "by preying on vulnerable Americans," including one by the Colombo crime family allegedly to defraud consumers with poor credit histories out of payments they believed were to secure loans.
Other charges alleged crime families'extorted money from labor union members, including the International Longshoremen's Association, and a concrete union in New York City.
While the arrests Thursday were an "encouraging, step forward in disrupting La Cosa Nostra's operations," the attorney general said, "Our battle against organized crime enterprises is far from over."
He said it remains a top priority, adding, "Members and associates of La Cosa Nostra are among the most dangerous criminals in our country. The very oath of allegiance sworn by these mafia members during their initiation ceremony binds them to a life of crime."