The actress, who played Abby Lockhart on the classic medical drama from 1999 to 2009, will reunite with former co-star Julianna Margulies on the CBS series, according to TV Line.
Tierney has landed the role of a character named Maddie, a self-made billionaire who is targeted by Eli (Alan Cumming) to fund and endorse Peter's (Chris Noth) campaign.
The character has been tipped to appear in as many as ten episodes of the upcoming season.
Friends actor Matthew Perry has also spoken of his desire to star on The Good Wife again following his guest stint as Mike Kresteva in the third season.
"It's been really fun to play a kind of sociopathic jerk lawyer," he said. "The Good Wife is one of my favourite shows, so it's all been very cool."
The Good Wife returns for a fourth season on Sundays at 9/8c in the fall. The series airs on More4 in the UK.