Lennox grew up in the Roland Park section of Baltimore, Maryland, and attended Waldorf School of Baltimore through 8th grade, and Kimberton Waldorf School in Chester County, Pennsylvania for high school. His family moved frequently during his early years, owing to his father's studies to be an orthopedic surgeon. As a youth, he played sports, mainly soccer and basketball. His brother, Matt Lennox (the Animal Collective song Brother Sport is directed at him), was a leading player on the high school basketball team and Noah was also a team member, playing as point guard.