The Under-21 team is effectively Watford's second-string side, but is limited to three outfield players and one goalkeeper over the age of 23 per game following the introduction of new regulations from the 2012–13 season.

Home fixtures are contested at the UCL Sports Ground, based in Bell Lane, Shenley, Hertfordshire.

Players who will qualify as under-21s in season 2024–25 (i.e. born on or after 1 January 2003) and who are outside the first-team squad.

Players born after 1 September 2006 qualify for the under-18 team.

Scholars who have signed a professional contract beyond the end of their scholarship have their contract expiration year listed in italics.