Arenas gave a simple, "Yes, sir" when Judge Richard Morin asked if he understood that he was pleading guilty to possessing a gun without a license, a felony charge that carries a maximum sentence of five years.
In the plea deal -- which Morin doesn't have to follow -- prosecutors will not seek more than six months in prison.
A source with knowledge of the investigation told FanHouse that Arenas may only receive probation unless something comes up in the pre-sentencing report that will be completed before Arenas is scheduled to be sentenced March 26.
"We are happy with the disposition," said Assistant U.S. Attorney Chris Kavanaugh.
Arenas and his lawyer, Ken Wainstein, refused to comment while entering and leaving the courthouse, but did release a statement shortly after the hearing.
"He accepted full responsibility for his actions, acknowledged that those actions were wrong and against the law, and has apologized to all who have been affected by his conduct," said Wainstein, in the statement. "Mr. Arenas appreciates the professionalism of the authorities handling this matter."
The troubles began, Kavanagh said, when Arenas got into an argument with Javaris Crittenton, referred to in the hearing as "the other player," over a card game on the team plane between late on Dec. 19 and into the early hours of Dec. 20.
"The other player suggested they have a fistfight," according the proffer of facts document read by Kavanagh. "Arenas declined, saying that he was too old to fistfight and instead that he would 'burn' the other player's vehicle and shoot him in the face."
Crittenton responded, Kavanagh said, by threatening to "shoot the (expletive) out" Arenas, including shooting him in his surgically-repaired knee.
On Dec. 21, Arenas arrived at Verizon Center with and walked over to Crittenton's locker. Arenas opened the backpack and placed four guns in front of Crittenton's locker with a note that said, "Pick 1."
"You said you were going to shoot me, so pick one," Arenas told Crittenton.
Crittenton said he didn't need Arenas' guns and that he had his own and then picked up one of the pistols and tossed it across the room.
Arenas told investigators both the incident on the plane and what happened in the locker room before practice were jokes.
Arenas, Kavanagh said, told an unidentified Wizards player to put the guns, now in a suitcase, into his car. When that player couldn't find Arenas' car in the parking garage, the player stored the guns in a secure spot.
Soon after, Wizards management found out that Arenas had brought guns the facility and told a member of the team's security personnel to secure the guns -- a .50-caliber gold-plated semi-automatic Desert Eagle, a 500 magnum Smith and Wesson revolver, .45 caliber, black semi-automatic Kimber Eclipse and a 9 mm Browning with an extended magazine -- and drive them to Virginia, where they were stored until the guns were turned over to investigators.
Crittenton, who was placed on paid leave by the Wizards, has not been charged, although his house was searched by investigators on Thursday. No guns were found, according to his attorney, Peter White.