The 28-year-old actor will play Dr. Sidney Miller, the assistant of evolutionary biologist Watts who the visitors want to destroy because of his discoveries, according to casting descriptions. Miller is suspicious about the V's, but has yet to discover all the information.
Harrison will make his first appearance in V's Season 2 premiere, scheduled for November. His casting was first reported by Entertainment Weekly.
Before Reaper, Harrison starred on the short-lived series The Loop and the 2008 film Deal.