Boeser, who grew up in Burnsville, Minnesota, is the youngest of three children to Duke and Laurie Boeser; he has a half brother, Paul, and sister, Jessica who has a Developmental disability. Duke was diagnosed with Parkinson's disease in 2010; he would also have a severe brain injury from a car accident a few years later, forcing him to stop working. To help support the family Laurie worked up to three jobs, including serving in a restaurant, office administration, and preparing tax returns. In early August 2014, while Boeser was in Slovakia for the Ivan Hlinka Memorial Tournament, a tragic car accident south of Minneapolis-St. Paul killed one of his closest friends and severely injured another, both fellow students and athletes at Burnsville High School. This followed the death of his grandfather prior to his first game in the USHL.