Hayley Kiyoko Alcroft was born on April 3, 1991, in Los Angeles, California, to Canadian figure skater and choreographer Sarah Kawahara and actor/comedian Jamie Alcroft. Her mother is of Japanese ancestry and her father is from Ohio and has English and Scottish ancestry. Kiyoko has two siblings, Alysse and Thatcher.
She began acting at a young age, appearing in national commercials for brands such as GM Onstar, Slim Jim, and Cinnamon Toast Crunch. Insisting on drum lessons at age six, she was writing drum charts for new releases and selling them in a local music store by age 11. At age 8, Kiyoko wrote a song called "Notice," which her father still urges her to release. She was elected student council president of her middle school and high school freshman classes and vice-president in her senior year. She attended Agoura High School and graduated in 2009. She was appointed "Commissioner of Entertainment" in her sophomore year and "Commissioner of Pep Rallies" in her junior year.
She created and choreographed "The Agoura High Step Team" which was faculty-approved as a school club under her direction. The team placed third at a Nationals competition in 2009. Upon graduation, she was accepted into Clive Davis School of Recorded Music at New York University but initially deferred until eventually declining due to career opportunities.
Kiyoko was discovered at the age of five when she went with her friend to a photoshoot. The director asked her to step in front of the camera, and she ended up in a national print ad for KnowledgeWare.
Children's cable TV network Nickelodeon spotted her at the Culver City Ice Rink, and she ended up featured in and narrating a short piece about children in sports called, "I'm Hayley, a Skater". Kiyoko continued to hone her skills in middle school plays and, in seventh grade, asked for an agent after seeing Eurasian girls like herself act in J. C. Penney commercials. She got her commercial agent and booked her first audition, claiming acting was always just something she did on the side to make money for college and music equipment. Kiyoko started the garage band Hede, named after her grandfather, in November 2007 and released five songs on Myspace and a music video for "Warehouse". The band performed locally on several occasions and split in 2009 after the remaining band members left for college. Her grandfather died in 2011. He was one of the biggest inspirations in Kiyoko's life.