The 45-year-old actress, who plays Edie Britt, is one of the original cast members in the ABC drama.
No details about her exit storyline have been released. However, her representative claimed that her final episodes would not air in the US "until April".
"She had a great time on the show and is looking forward to her next project," her rep told People.
Desperate Housewives returns to Channel 4 on February 25 at 10pm.