Warburton was born in Paterson, New Jersey, the son of orthopedic surgeon John Charles Warburton, Jr. and Barbara Jeanne Gratz (an actress credited as Barbara Lord). He and his three sisters, Mary, Lara, and Megan, were raised in a "very religious" and "conservative" Catholic family in Huntington Beach, California, where he attended Saints Simon and Jude Catholic School. He later attended Servite High School (in Anaheim, California), and later transferred to Newport Harbor High School (in Newport Beach, California). He studied marine biology at Orange Coast College in Costa Mesa, California, but dropped out to pursue modeling and acting.
- Kronk from The Emperor's New Groove and Ninja of '05 in Randy Cunningham: 9th Grade Ninja look, act, and sound similar to each other.