The Starships singer was due to play the 4 Music stage today and tomorrow (18 and 19 August) but is reportedly unable because of "vocal issues".
According to Digital Spy, festival organisers released a statement that read: "Miss Minaj's band and crew have all arrived in the UK ahead of the performance at the festival this weekend, however as the artist herself boarded her flight from New York on Friday 17th August, she felt unwell again.
"This is despite having thought she had overcome her vocal cord issues from earlier in the week.
"Having revisited her doctor she has now been advised to rest for a week, which unfortunately means that she is no longer able to perform at V Festival."
Nicki had been struggling with her voice earlier this week - and after two New York gigs with rapper Drake, tweeted: "It's official, my voice is GONE!"
V Festival organisers said that they wished Minaj a "speedy recovery", and announced that LMFAO would perform in the slot instead.
The Young Money singer is due to tour the UK later this year.
Watch MTV News on the hour every hour on MTV - Sky Channel 126 and Virgin Channel 134