The 31-year-old singer wore a pleated purple Pamella Roland gown and debuted her new blonde bob on the red carpet.
The Voice star, who recently released her fourth studio album Lotus, revealed her new look at an awards bash a few months ago and spoke of loving her generous cleavage and "booty".
Yesterday evening saw Justin Bieber arrive at the ceremony with mother Pattie Mallette and take home three awards including the 'Artist of the Year' award.
Other guests included Nicki Minaj and Taylor Swift.
See more stars arriving at the American Music Awards here.
Copyright: Rex Features Jim Smeal / BEI