She and her sister wrote a book called Disney's Once Upon a Time with Mary-Kate & Ashley.
She also wrote another book called Mary-Kate & Ashley's Walt Disney World Adventure (Mary-Kate and Ashley in Action). She also played Natalie in the "Help!" episode of the ABC TV show Samantha Who? and appeared in All My Children. Mary-Kate retired from acting in 2012 to focus on her fashion career with Ashley.
Elizabeth Olsen is her younger sister.