Dele Alli set Spurs on their way in the 16th minute after a mistake from Watford goalkeeper Orestis Karnezis.
England striker Kane then converted Kieran Trippier's cross three minutes after half-time to seal the three points.
Tottenham, who remain fourth, moved five points clear of fifth-placed Chelsea while the Hornets are without a win in seven games.
But how did the rest of Mauricio Pochettino's men perform?
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