This is a chronology of events related to Ashlee Simpson in the year 2003.
- July 22: The soundtrack to the film Freaky Friday, featuring a song recorded by Ashlee titled "Just Let Me Cry", is released in the U.S.
- August 19: Ashlee appears in the first episode of her sister Jessica's reality series Newlyweds, also featuring Nick Lachey. (The episode's title is "Chicken By The Sea".)
- October 14: Ashlee appears in the ninth episode of Newlyweds, titled "Newlyweds Birthday".
- December 11: The Freaky Friday soundtrack is certified gold.