Powell had been tweeting about not feeling well in recent weeks.
"’Julie & Julia’ became an instant classic and it is with gratitude for her unique voice that we will now remember Julie’s dazzling brilliance and originality," Judy Clain, the editor-in-chief of Little, Brown and Co., said in a statement announcing her death.
"We mourn her loss with her husband Eric and her family. We are sending our deepest condolences to all who knew and loved Julie, whether personally or through the deep connections she forged with readers of her memoirs. She was a brilliant writer and a daring, original person and she will not be forgotten."