The 'Eureka' star will play Tripp, the head of a community militia, reported Ace Showbiz.
Executive Julie Plec said, "He's in town to give Sheriff Forbes a run for her money."
Ferguson, aside from playing Jack Carter in 'Eureka' between 2006 and 2012, has appeared in 'Haven and Primeval: New World'.
The CW's supernatural drama recently cast newcomer Gabrielle Walsh as Sarah, a character who arrives in Mystic Falls with a "shady" agenda.
'The Vampire Diaries' resumes in the US on October 2.