The sister of former NBA star Sebastian Telfair, who awaits sentencing after being convicted in Brooklyn of weapons possession, was arrested by the FBI Monday for allegedly threatening the former hoopster’s estranged wife.

Octavia Telfair, 32, is accused of making violent threats against Samantha Telfair, who had testified in Brooklyn Supreme Court that she had seen the former Portland Trailblazer with multiple weapons, including a submachine gun he had on him when he was arrested two years ago.

The Coney Island woman faces a charge of transmitting an interstate threat to injure a person by phone to a witness, identified in a federal complaint as Jane Doe, who had testified at the former player’s trial.

A source told The Post that the person Octavia allegedly threatened was Samantha, who had identified some of the guns found in her hubby’s pickup truck.

The estranged wife was inundated with about 50 threatening phone calls from a telephone number that appeared as “No Caller ID,” according to the criminal complaint and the source.

In one phone call, which Samantha recorded, Octavia screamed that “Jane Doe was ‘gonna die,’ and/or that Jane Doe was going to have to live with a ‘rearranged face,’” according to the document.

Octavia also said she would “kill all of y’all bitches,” referring to the victim and her mother, aunt and sister, according to the complaint.

In another phone call recorded by Samantha, Octavia said she was “on a mission.”

“F— your kids, bitch. They can die too. Die, kids, die,” she is alleged to have said.

Sebastian, a basketball prodigy out of Abraham Lincoln High School in Brooklyn who was selected 13th overall in the 2004 NBA draft by the Trailblazers, was convicted of gun-possession charges in April.

In 2007, cops found a .45-caliber handgun in his car during a traffic stop on the Bronx River Parkway after pulling him over for going 77 mph in a 45 mph zone and driving with a suspended Florida license.

Then with the Minnesota Timberwolves, Telfair claimed he had no idea where the gun came from. He ultimately pleaded guilty to criminal possession of a weapon and copped to three years’ probation in 2008.

In 2017, he was arrested again after cops found three loaded pistols, a gas-operated submachine gun, ammo, extended magazine and a ballistic vest in his Ford F-150 pickup truck.

He had been driving through Brooklyn without his headlights on, and then parked illegally on an Atlantic Avenue median, drawing the cops’ attention.

Telfair’s mistress Caterina Scotto also testified during the trial, where she said she saw him with a gun on multiple occasions — and giggled as she recalled he would call firearms “biscuits.”

Octavia Telfair will appear in Brooklyn federal court later Monday.

Her brother is facing up to 15 years in jail. His sentencing is scheduled for June 18.