Barnett and his sister were adopted;[3] his adoptive mother is from Utah and is of Swedish descent,[4][5][6] while his adoptive father is a boat builder from Minnesota.[7][3] He was raised on a sailboat in Florida until he was seven.[6] He discovered theatre when he was six years old, and performed in many operas and musicals.[7] Barnett is a graduate from Booker High School.[8] He participated in the Carnegie Mellon Musical Theater Summer Program.