The Scottish star – who has already featured on Professor Green’s chart-topping single Read All About It – will receive her prize at the event in February at London’s O2 Arena.
She follows in the footsteps of stars such as Adele, Jessie J and Florence and the Machine in taking the annual award.
Sande, from Aberdeen, has written hits for Chipmunk and Wiley, and has credits for album tracks by Cheryl Cole, Susan Boyle and Tinie Tempah.
She is due to release her debut album, Our Version of Events, in February.
Sande said: “To win a Brit Award so early in my career is beyond a dream come true. I am overwhelmed to be the recipient of such a prestigious award.”
The winner was chosen by a panel of music experts as the act most likely to make it big in 2012, with more than 100 acts considered for the title. Other Brit award nominees will be announced on 12 January.