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 29th
Watford v Burnley
Saturday March 30th
Peterborough v Cardiff
Monday April 1st
Cardiff v Blackburn
Tuesday April 2nd
Hull v Watford
Saturday April 6th
Watford v Cardiff