The rapper and singer (37), announced the news in a post on Instagram featuring a photo of herself cradling her bump.
Minaj, known for hits including Super Bass and Anaconda, fuelled rumours she was pregnant by replying to a fan in May.
Minaj, who was born in Trinidad, married 42-year-old Kenneth Petty last year.
Their relationship proved controversial after it emerged Petty had been convicted of attempted rape in 1995 and later spent seven years in prison for manslaughter.
