The pair will play lovers who enter a fortune-teller's lair and face "devastating consequences" in an upcoming episode of the CBS series, TVLine reports.
Kebbel played Lexi in The Vampire Diaries and has also appeared in 90210, True Blood and Jesse Metcalfe movie John Tucker Must Die.
Amell's filmography includes Pretty Little Liars, How I Met Your Mother and Alcatraz as well as Revenge, in which he plays Adam.
Kendall Jenner recently announced that she will make her acting debut in Hawaii Five-O's third season, while Pulp Fiction actor Ving Rhames has also signed up for a role.
Hawaii Five-O, which stars Alex O'Loughlin, Scott Caan and Daniel Dae Kim, returns to CBS on September 24.