Her representative says in an email that Minaj will have to back out of her shows on Saturday and Sunday because of "strained vocal cords."
Minaj performed a free concert in New York City on Wednesday, though she had been advised by her doctor to rest.
Her rep now says her voice is "worse," and that recent X-rays show that the singer-rapper must "rest her voice for a few days."
The two-day V Festival also features The Killers, David Guetta, LMFAO and The Stone Roses.
Minaj performed for more than two hours at her New York show. It featured Drake, Lil Wayne and Foxy Brown.