Other newly-added acts include Rita Ora, Newton Faulkner, Childish Gambino, Sub Focus, The Feeling, Stooshe, Cover Drive, The Rifles and Angel.
Additional tickets for the festival go on sale this Friday, April 27 at 9am.
Wretch 32 said: "I'm buzzing to be back at V Festival again this year. Last year was big, and I'll be looking to top it this year by performing my new tracks to the V crowd.
"I will also be looking to get a little meet with Nicki Minaj… if I'm lucky!"
Knight added: "It has been a while so I am chuffed to be back on stage at V this year.
"I have spent the last few years enjoying all the action as a punter. This year it's time to do what I do best - and that's rocking a crowd!"
Stooshe said: "Really looking forward to V Festival this year. We attended last year so to be performing this year is amazing! The line up is wicked and it feels great to be a part of it. So excited!"
V Festival 2012 takes place at Hylands Park, Chelmsford and Weston Park, Staffordshire on August 18 and 19 and is headlined by The Stone Roses and The Killers.
Noel Gallagher's High Flying Birds, Tom Jones, Snow Patrol, Ed Sheeran, David Guetta and Tinie Tempah are among the artists performing over the weekend.
> Wretch 32 interview: 'My next album is even better'
Watch the Stooshe 'Love Me' music video below: