Watt was born in Waukesha, Wisconsin. He attended Pewaukee High School in Pewaukee, Wisconsin. He played both defensive end and tight end. Watt also lettered in baseball, basketball, and track during his high school career. As a senior, Watt was state champion in the shot put. In addition, he played (ice) hockey for ten years between the ages of 3 to 13 before he quit and eventually became a multi-talented student athlete in the four other sports listed above. He has two younger brothers, Derek Watt, who currently plays for Wisconsin, and TJ Watt, who on February 6, 2013 signed his letter of intent to play at Wisconsin.