Leicester City reclaimed second place and equalled a club record of seven successive top-flight victories thanks to second-half goals from Jamie Vardy and James Maddison.
Harvey Barnes hit the side-netting for the hosts on 24 minutes, before bringing a sharp save from Ben Foster 12 minutes later.
At the other end, Gerard Deulofeu flashed a powerful free-kick wide before setting up Will Hughes for a blocked shot on the stroke of half-time.
Brendan Rodgers' side got the breakthrough 10 minutes after half-time. Jonny Evans was fouled by Adam Masina and Vardy converted the penalty, scoring for the seventh Premier League match in a row.
Maddison then struck a second goal for the hosts deep into stoppage time, breaking through and finding the bottom right corner.
Leicester climb above Manchester City into second place on 35 points, while Watford remain bottom on eight points.
Leicester City: 8 Dec v Aston Villa (A)
Watford: 7 Dec v Crystal Palace (H)