The club have reported that all 2,200 tickets available to Cardiff fans have been sold and that no more are expected to be made available.
The match is live on Sky TV with a 5:20pm kick off on Saturday 6th April.
City currently lead Watford by 9 points.
The next fixtures for both clubs are:
Friday March 29thWatford v Burnley
Saturday March 30thPeterborough v Cardiff
Monday April 1stCardiff v Blackburn
Tuesday April 2ndHull v Watford
Saturday April 6thWatford v Cardiff
Source: Cardiff City Online