Spencer attended the University of Houston for four years. After doing a number of independent films, he met Amanda Winn-Lee, who suggested he audition for anime English dubbing at ADV Films. Spencer first landed a supporting role of Prime Minister Mikoshiba in "Super Atragon", then a leading role of Takateru in "Suikoden Demon Century." In August 1996, Spencer was cast as the lead role of Shinji Ikari in "Neon Genesis Evangelion". After ADV Films' collapse, Funimation acquired the rights to the "Rebuild of Evangelion" movies. As part of Funimation's goal to get the service of the original voice actors from shows and movies they acquired distributing rights for, Spencer reprised Shinji in the movies.