The actress will play Vanessa, a reformed bad girl who falls for one of the show's male characters, according to TV Line.
Kebbel previously appeared on The Vampire Diaries as Lexi.
In October 2010, Vampire Diaries producer Kevin Wiliamson suggested that Lexi could return to the CW series in flashbacks despite being killed by Damon (Ian Somerhalder) on the show's first season.
Actress Dina Meyer also recently signed on to appear in 90210, playing a modelling agent who becomes interested in the career of Matt Lanter's character Liam.
90210 airs Tuesdays at 8/7c on The CW.