If anything, the margin of defeat flattered the visitors as the Hornets carved out a succession of opportunities and could easily have scored more goals had their finishing been better and Addicks goalkeeper Neil Etheridge not made some fine saves.
As it was, Charlton were effectively beaten by half-time after their opponents had opened up a three-goal lead by the break thanks to goals from Craig Cathcart, Troy Deeney and Odion Ighalo.
With the game all but won, the Hornets took their foot off the pedal to a degree in the second half, while remaining comfortably in control. But they did score twice more as Ighalo headed in a corner before Daniel Tozser fired in the fifth late on from a free-kick.
One of the recent criticisms of Watford has been their slow start to matches but there was a much higher intensity to them and their early efforts were rewarded with a goal in the 15th minute.
Charlton failed to clear a corner properly and when Miguel Layun crossed from the right, the ball was allowed to bounce up invitingly for Cathcart to fire the ball into the roof of the net.
Prior to the goal though, Deeney had gone close on three occasions and should really have scored when he was picked out by Ighalo’s cut-back, but he put his attempted finish too close to Etheridge.
But the Watford captain, who was celebrating his 200th appearance in all competitions, was to get on the scoresheet in the 25th minute when a lofted pass from Gabriele Angella put him through on goal and he held off Andre Bikey before slotting home.
Charlton, who had seen Johan Berg Gudmundsson force Heurelho Gomes into an early save, were all at sea defensively and it took a fine save from Etheridge to prevent Ighalo from making it 3-0 before the half-hour mark.
But Ighalo did net a third in the last minute of the opening half, netting from close range after Layun had released Juan Carlos Paredes on the overlap to deliver a low cross.
Watford continued where they had left off in the first half after the restart and they made it 4-0 in simplistic fashion in the 58th minute when Tozser delivered a precision corner and Ighalo rose unchallenged on the edge of the six-yard box to thump a header into the back of the net.
Deeney would have doubled his tally in the 73rd minute, but his 20-yard curling shot was kept out by a great stop by Etheridge.
However, the Addicks keeper was to be beaten one last time when Tozser curled a 25-yard free-kick across him and into the far corner with what was effectively the last kick of the game.