Joao Pedro’s deflected effort gave the Hornets an early lead in front of incoming head coach Rob Edwards.
But familiar defensive issues contributed to the hosts’ downfall as James Maddison’s leveler and doubles from Vardy and Barnes condemned them to a 26th Premier League loss of a miserable campaign.
The Foxes’ victory was relatively straightforward after their ongoing set-piece frailties were exposed early on and keeps them on course for a fifth-successive top-half finish.
Watford’s latest defeat equals the overall top-flight record of 15 home reverses in a season and leaves former Forest Rovers boss Edwards in little doubt about the major summer overhaul required. -AP