Ironically, the actress, who is a breast cancer survivor, will portray a professor who undergoes experimental treatment for the disease.
Nixon will be the second Sex & the City star to hit the stage in New York this winter - Kim Cattrall will lead the cast of a revival of Noel Coward's Private Lives in November (11).
Wit will begin previews in January at the Samuel J. Friedman Theatre.
Nixon won a Tony Award in 2006 for her role in David Lindsay-Abaire's Rabbit Hole.
She is also playing a cancer victim in TV series The Big C.