Watford's first team will take on St Albans City on Saturday, July 26.
The Championship side have been looking for an opponent over the weekend of July 25-27 and were considering a double header in Scotland.
But it was confirmed this afternoon the sides will face each other at Clarence Park at 3pm.
Tickets will be £10 for adults, £5 for concessions (over 65s, students, unemployed and 16-21 year olds), £2 for under-16s and under-12s get in for free.
Tickets can be purchased in advance and collected on the day by calling St Albans’ club office on 01727 848914.
St Albans were promoted to the Conference South last season via the play-offs and are co-managed by James Gray and Graham Golds.