Sophie (voiced by Emily Mortimer), an average teenage girl working in a hat shop, finds her life thrown into turmoil when she is literally swept off her feet by a handsome-but-mysterious wizard named Howl (voiced by Christian Bale), and is subsequently turned into a 90-year-old woman (voiced by Jean Simmons) by the vain and conniving Wicked Witch of the Waste (voiced by Lauren Bacall). Embarking on an incredible odyssey to lift the curse, she finds refuge in Howl's magical moving castle where she becomes acquainted with Markl, Howl's apprentice, and a hot-headed fire demon named Calcifer (voiced by Billy Crystal). Sophie's love and support comes to have a major impact on Howl, who flies in the face of orders from the palace to become a pawn of war and instead risks his life to help bring peace to the kingdom.

Based on the novel by Diana Wynne Jones.