The Essex born singer-songwriter has topped the names longlisted last month for the title of the act most likely to succeed in the year ahead.
The star, whose real name is Jessica Cornish, said that she was "overwhelmed" by the accolade, adding: "It feels amazing to be accepted on such a broad scale. I know I'm doing something right and I've got to keep doing it. It's an honour."
After discovering the news, the 'Do It Like A Dude' singer posted on her Twitter page: "Mmaaaann!!! Today is crazy!!! I’ve been up since 4.30am. Sssoo happy! Soo busy! Thank you BBC and everyone who voted. (sic)"
Jessie J was also recently announced as the winner of this year's Critics' Choice prize at the Brit Awards.
The top five acts for this year's BBC Sound of 2011 are listed below:
1. Jessie J
2. James Blake
3. The Vaccines
4. Jamie Woon
5. Clare Maguire