Knight will play a 'political operative' on the CBS drama's current fourth season, Entertainment Weekly reports.
© WENN
© CBS
The actor is best known for playing Dr George O'Malley on Grey's Anatomy between 2005 and 2009, and last year appeared in an episode of Law & Order: Special Victims Unit.
Last month, it was announced that Stockard Channing (Grease, The West Wing) will appear on The Good Wife, while Michael J Fox is also due to reprise his role as attorney Louis Canning in a future episode.
The Good Wife continues on CBS on Sunday nights in the US and airs on More4 in the UK.
The show's star Julianna Margulies - who plays Alicia Florrick - is currently involved in a real-life legal dispute with her former management team D/F Management.
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Watch a preview for The Good Wife below:
