Van Outen originally played Roxie Hart in the 2001 West End production at the Adelphi Theatre and starred in the role on Broadway in 2002.
She was due to take on the role of Velma Kelly – the nightclub singer accused of murdering her husband and sister – from 24 September until 17 November but will now join the cast at a later date. Her replacement will be announced in due course.
The company also features Alexandra Burke as Roxie Hart, Duncan James as Billy Flynn, Mazz Murray as Mama Morton and Paul Rider as Amos Hart.
Van Outen's other theatre credits include Tell Me on a Sunday, Legally Blonde and Rent. In 2012 she reached the final of Strictly Come Dancing.
Chicago returned to the West End in March this year. It originally opened in London in 1997 and ran for 15 years. Read our review of the show's return here.