The daughter of an NYPD officer killed on 9/11 was sworn into the force Thursday, after completing training to follow in her father’s footsteps.

Brittney Roy, a Massapequa Park native, took an oath along with 473 new recruits at the police academy in Queens.

She is the daughter of Sgt. Timothy Alan Roy, a Massapequa Park resident who was assigned to the surface transit enforcement division when he was killed in the World Trade Center attacks.

“She’s really, really thrilled to carry on the legacy of her father, and I think that’s great,” NYPD Commissioner James P. O’Neill said of Roy during a news conference. “Her dad was a courageous guy.”

Roy was 7 when the Twin Towers were struck. Her father had been in traffic court and rushed to the scene after hearing about the attack, she said.

He was last seen near the South Tower shortly before it collapsed. He was 36.

“Approximately that March, the day before St. Patrick’s Day, which was his favorite holiday, he was found, and we were able to bury his body,” she said during the news conference.

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Roy said she had long wanted to become a police officer like her father, even during her time studying at the University of Rhode Island.

Roy’s stepfather Tom Christ is a retired NYPD officer and said the family is proud of Brittney Roy for achieving her goal.

“She’s been talking about this a long time,” he said. “She’s a great kid and she’s going to do fine.”

Roy took exams for both New York City and Suffolk County law enforcement before deciding on the NYPD.

Now a probationary officer, Roy and her fellow graduates will begin six months of training, NYPD officials said.

“Growing up in the police department, you really see the true heroes they have,” she said. “It’s always been a dream to be one of them.”