Jackie Lynn Thomas (voiced by Grey Griffin) is a skateboarding classmate who has been Marco's crush since kindergarten. She and Marco start dating in the season 2 episode "Bon Bon the Birthday Clown", but ended their relationship in the season 3 episode "Sophomore Slump"
She has short blond hair with a streak of blue, aqua eyes, and freckles. She wears a green and white shirt, a golden seashell necklace, cyan shorts, green and white kneesocks, and blue and white shoes. In "Brittney's Party", she wears a flower in her hair, a purple top, blue jeans and beige boots.
Jackie is a cute and kind girl who is shown to enjoy and have a talent for skateboarding. She is unaware of Marco's crush on her and is generally indifferent towards him, though she has been impressed with him a few times.
- In "Freeze Day", it is shown that Jackie has known Marco since kindergarten.