He faces 25 years to life in prison for what DNA evidence has supported happened to the now 14-year-old girl.
Jurors issued the verdict on Thursday in Long Island court. The charges stem from an incident in which Maraj assaulted the 11-year-old child of his now ex-wife, threatening her younger brother (8-years-old at the time) with violence should he speak up. The defence lawyer claimed the allegations were fabricated by the child's mother in order to extort $25m (£19m) from Nicki Minaj.
In closing arguments Monday, Nassau County Assistant District Attorney Emma Slane called that claim "absolute absurdity".
The accuser, now 14, girl testified that Maraj, 38, anally raped her at one point, slapped her in the face and ordered her to remain mute about his actions.
The prosecutor said DNA evidence recovered from the girl's pajama trousers was linked to Maraj.
"Why tell this lie?" "It's real life with real-life consequences".
The victim's younger brother, now 10, also testified that he saw Maraj with his "private parts" on his sister when he walked into her bedroom in 2015. "This is an old-fashioned shakedown".
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. David Schwartz said the woman contacted Maraj's lawyer asking for $25 million so the "charges could just go away", however, the mother denied she made up the allegations. She testified that Maraj referred to her as a "puppet" and physically assaulted her if she rejected his advances.
Nicki Minaj was not called as a witness, and she has not publicly commented on the case.
Born Onika Tanya Maraj, Nicki Minaj grew up in New York City.
The Associated Press does not identify alleged victims of sexual assault, and is not identifying the girl's mother to protect her daughter's identity.