Haley Kay Long (Amy Bruckner) is Jake's intelligent, goody-two-shoes little 8-year-old sister.
Like Jake, Haley also has dragon powers, although hers are not fully developed yet despite the fact they start developing in an earlier age than Jake's (In "Legend of the Dragon Tooth", Susan Long explains that dragon girls develop their powers earlier). She takes pride in exposing Jake's mischievous behavior to their parents, as well as showing off her own "superior" talents. Normally the audience only sees little parts of her dragon form, such as her wings and tail. In "Family Business", her full dragon form is revealed, and she begins her own dragon training under Sun Park's guidance. She has taken many aspects of her training with Sun to be applied in her daily life, which puts her at odds when paired with more "average" kids her age. She also seems to take pleasure in making her brother look bad as a dragon. However, she is starting to show more respect towards Jake. In fact in the episode "Family buisness" Haley openly admit's that Jake is a better dragon than her and in the episode "Being human" where she take's Jake's place as the american dragon she quickly suffer's a breakdown and realises how hard it is for her brother to balance his human life with his duty as the American dragon.
It is revealed in "Haley Gone Wild" that she has never gotten in trouble (until the end of the episode) and she says doing something bad is against her nature. She is present in "Homecoming", when Rose betrays her brother before destroying the Huntsclan. She witnessed Jake trying to save her before he destroyed all of the skulls in a furious rage. She also takes part in the final battle with the Dark Dragon rescuing her grandfather, re-capturing Councilor Chang and witnessing Rose's return to help as well as the Dark Dragon being trapped for a thousand years in another dimension.
It is revealed that she was named after Haley's Comet, her mother loved the name "Haley" when she was dating her father.
- According to producers Matt Negrete and Eddie Guzelian, Haley was named after Eminem's young daughter, Hailie, due to the creator being a big fan of the rapper.
- Concept sketches show that Haley was originally going to be named Brittany.