Jackie was born on September 11, 1977, in Los Angeles. Her father is a retired LAPD officer.
Prior to Gravity Falls, Jackie was a production assistant for shows such as SpongeBob SquarePants and Camp Lazlo, later moving onto voice work on Adventure Time. Writing stints soon followed on shows such as the Disney show Fish Hooks with Justin Roiland and The Marvelous Misadventures of Flapjack, as well as voicing Sally Syrup on the latter show, who plays opposite of the titular Flapjack, voiced by Thurop Van Orman (the voice of Gideon Gleeful).
Buscarino is a frequent collaborator with Justin Roiland outside of Gravity Falls. She is currently a producer on Steven Universe (also providing the voice of Vidalia), and a writer/voice actor on Adult Swim's Rick and Morty, once again collaborating with Roiland.
From 2010 to 2013, along with Roiland and Ryan Ridley, she was one of three members of the highly successful podcast The Grandma's Virginity Podcast.