The actress has signed up to play a lobbyist in several episodes of the show, TV Line reports.
Her character Stacie Hall ends up becoming a rival for Eli (Alan Cumming) and starts stealing his clients.
The Good Wife's executive producers Robert King and Michelle King admitted: "We love Amy.
"We sometimes have dreams of switching all the actors from The Wire and Strangers With Candy. The next best thing is to have Amy playing Eli Gold's nemesis."
As well as starring in Strangers With Candy, Sedaris has had guest roles in shows like Sex and the City, The Closer and Raising Hope.
Her movie credits include Jennifer's Body, Bewitched, Elf and School of Rock.
Anika Noni Rose recently signed up to reprise her role as Wendy Scott-Carr in an upcoming episode of The Good Wife.
The show airs on Sundays at 9/8c on CBS.