Chief Ronal Serpas says the suspect turned himself in to authorities in the 6th District.
WWL-TV reports the teenager's family saw his picture in the media and told him to turn himself in.
The suspect confessed to the crime, according to Serpas, who added that two suspects remain at large.
Chief Serpas is urging others involved to turn themselves in as well, saying "We know who you are."
Serpas says the 15-year old has a "very minor" criminal record. He calls it a "crime of opportunity" and hopes the suspects will be tried as adults.
Police say they have started to put together some of the pieces in the crime. They recovered the victim's silver Honda Accord. It was found abandoned in the 800 block of North Dorgenois by a police officer around 7 a.m. Wednesday.
The victim in the case says she was abducted from the 1200 block of Eighth Street at gunpoint and was driven around and sexually assaulted. Police say she was brought back to the area and let out, though the suspects robbed her and stole her car.
NOPD officials say the investigation continues.