Preet Bharara, the Manhattan federal prosecutor, said he was "disappointed" but did not say whether he would seek a fifth trial.
"We are evaluating how to proceed and, in the near future, will inform the court."
Prosecutors were desperate to put Gotti away after three other trials over the last half decade ended with juries failing to reach the required unanimity on a verdict.
After 11 days of deliberations, the jury declared themselves evenly split on all charges.
Gotti was accused of involvement in three Cosa Nostra slayings and large-scale cocaine dealing during a decades-long racketeering career with the Gambino crime family in New York and Florida.
Throughout the 10-week trial, Gotti's lawyer insisted his client had long quit the mob, or "the life."
Carnesi accused the government of concocting a case based on testimony from convicted Mafia turncoats ready to say whatever was required in exchange for lighter sentences.
Jurors told journalists after the trial ended that they had been suspicious immediately of the star prosecution witness, a confessed mob hitman called John Alite, who was once a close Gotti friend.
In one of the tensest moments of the marathon trial, Gotti lost his temper, yelling at Alite: "You fag! Did I kill little girls? You're a punk. You're a dog. You're a dog. You always were a dog!"