They join the already-announced Kanye West and Drake, who will also take the stage September 12th.
Bieber said in a statement, "I'm excited to be performing at the VMAs. It is all still unbelievable, because last year I went for the first time and no one knew who I was. Just really shows that dreams can come true and what incredible, dedicated fans I have. I'm a lucky guy and grateful. Now I just want to get on that stage, have some fun in front of my heroes, because at the end of the day I'm still a kid and still a fan."
B.o.B. added, "It's very special to me. I think it's a lot more special than the success of the singles, because this reflects the work I've put in over the years and the word of mouth I've helped create. It's definitely amazing. I'm trying to find the words to explain it, but I can't. It's inexplicable. I'm a real simple man, so, you know, I accept every gift with generosity and gratitude."
One artist who was seemingly left out is Ke$ha, who was only asked to present, rather than perform. She joins previously-announced presenters Ashley Greene, Nicki Minaj, Emma Stone, Penn Badgley, Trey Songz, Selena Gomez and Ne-Yo.
Additional performers and presenters, as well as the VMA host, will be announced in the weeks to come, so stay tuned!