He faces no less than 25 years in prison with a maximum sentence of life.
Jurors delivered their verdict on Thursday (November 9) in Nassau County Court.
Maraj was found guilty of sexually assaulting his stepdaughter when she was just 11 years old.
In closing arguments Monday, Nassau County Assistant District Attorney Emma Slane called that claim "absolute absurdity". In addition, a forensic expert called by prosecutors confirmed that a stain on the girl's pajama trousers matched Maraj's DNA profile.
Throughout the trail it was rumoured that Nicki may have been called as a witness in her brother's defence, but neither she, nor her brother, took the stand. "It's real life with real-life consequences". Both the girl, now 14, and her 10-year-old brother testified during the trial.
"It's all about money and it's all about revenge", he told the jury. The mother denied the accusation.
The defense had also claimed during the month-long trial that the allegations had been created to extort $25 million from the man's famous sister; they also had to walk back a claim that Minaj would testify on her brother's behalf.
James R Ray III, a civil attorney who briefly represented the mother, testified that he did demand a $25m legal settlement from Jelani Maraj after he had been arrested, but said the girl's mother was unaware of the demand. The girl testified that Maraj treated her as his own daughter before he began raping her. He said when Maraj confronted him a short time later, the sicko slapped him across the face, and threatened he would never see his mother again if he told anyone what happened.
Minaj has not yet responded to the news. Forbes said she was No. 16 in earnings among rappers in 2017 with $16 million.
The Associated Press does not identify alleged victims of sexual assault, and is not identifying the girl's mother in order to protect her daughter's identity.