The Back to the Future star has previously appeared in three episodes as attorney Louis Canning.
The Good Wife co-creator Robert King confirmed to TV Line that Fox will reprise his role in "three or four episodes".
Earlier this year, the actor received an Emmy nomination for his performance as Canning, but ultimately lost out to Harry's Law guest star Paul McCrane.
Other actors confirmed to appear in the third season of The Good Wife include Lie to Me's Monica Raymund, Dazed and Confused's Parker Posey, House's Lisa Edelstein and returning guest star Dylan Baker.
The legal drama's third season begins on Sunday, September 25 at 9/8c on CBS.
> Good Wife exec: 'Kalinda will be more human'
Watch a promo for the new season of The Good Wife below: