Campbell is the son of Jennifer and Tony Campbell, who played basketball at Luther College. They named their son after Tiger Woods. Campbell grew up in Cedar Rapids, Iowa. He attended La Lumiere School in La Porte, Indiana, which he credits for his "entry into manhood", adding, "it’s a place where you can learn how to be a good teammate." In his sophomore season, he led La Lumiere to the Dick's Sporting Goods championship and a 29–1 record while averaging 11.3 points and 7.8 assists per game. Following his sophomore season, Campbell reclassified to the class of 2018 because he was ahead academically and felt he was ready for college basketball. As a senior, Campbell averaged 15.5 points and 7.2 assists per game. Campbell initially committed to DePaul on May 8, 2017, but he withdrew his commitment in September. In February 2018, he signed with UCLA.
