The forthcoming drama will star Kristin Kreuk (Smallville) as cop Catherine Chandler and Jay Ryan (Terra Nova) as 'beast' Vincent Keller.
Overton will play Claire, a medical student who bonds with Catherine's ally Evan (Max Brown), according to TV Guide.
The character will first appear in Beauty and the Beast's fourth episode - expected to air in November - and may recur later in the season.
The 34-year-old star recently played Rikki - a love interest for werewolf Alcide (Joe Manganiello) - on HBO's True Blood and has also appeared on episodes of Psych, Criminal Minds and CSI: NY.
Jeremy Glazer (Castle, Bones) has also been cast on Beauty and the Beast as a medical student searching for his missing fiancée.
Beauty and the Beast premieres on Thursday, October 11 at 9/8c on The CW.
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Watch the stars of Beauty and the Beast discuss the series below: