McDaniels was born Sep. 29, 2000. His brother, Jalen, was selected by the Charlotte Hornets in the 2019 NBA Draft. Jaden is also the cousin of former NBA player Juwan Howard. His father, Will McDaniels, and mother, Angela Jackson, are originally from the Windy City, Chicago. Jaden played high school basketball for Federal Way High School in Federal Way, Washington. He was teammates with his older brother Jalen and helped the school win its second straight Class 4A state title during his freshman campaign. McDaniels' stock began to rise from his junior campaign onward, and as a senior, he averaged 23.3 points, 10.0 rebounds, four assists and two blocks per game. He finished high school as the 2019 Class 4A Player of the Year and Washington Gatorade Player of the Year. He also played in the McDonald's All-American Game and the Jordan Brand Classic. For college, McDaniels attended Washington and averaged 13.0 points, 5.8 rebounds and 1.4 blocks as a freshman. After that season, he declared for the 2020 NBA Draft.