The result lifts the Blues back up to fourth in the table, after they were temporarily leapfrogged by Manchester United.
Nigel Pearson’s side remain a point above the relegation zone but have played a game more than Aston Villa, who travel to Liverpool on Sunday (16:30 BST).
Olivier Giroud opened the scoring for the Blues, latching on to Ross Barkley’s clever pass and steering a left-foot shot into the bottom right corner.
While Watford worked hard to contain the hosts they offered little to suggest they were capable of a first win at Stamford Bridge since 1986.
And they fell further behind before the break, with Etienne Capoue’s rash challenge on Christian Pulisic resulting in a #Chelsea FC penalty that Willian duly converted.
Thereafter it was relatively plain sailing for Frank Lampard’s side, who rounded off the scoring when Barkley found the top left corner from Cesar Azpilicueta’s cross.
The Blues have now won three of their four games since the top flight resumed in June.
Manchester United’s thumping victory against Bournemouth had seen Chelsea drop out of the top four places for the first time since 26 October.
But this was the perfect response from Frank Lampard’s side who were brimming with energy throughout and appeared galvanised by Wednesday’s lacklustre defeat at West Ham.
The Blues made four changes to their starting XI and looked considerably more assured defensively while Willian – who scored a penalty in his third consecutive game – Barkley and Pulisic provided the thrust going forward.
England midfielder Barkley was particularly impressive, demanding the ball in tight areas and then restricting his number of touches to get out of trouble and maintain Chelsea’s attacking momentum.
Chelsea’s opener was the perfect example as he controlled and swivelled away from a defender in one movement and then sliced open the Watford defence with his next touch.
Barkley, who played more attacking passes (47) than any of Chelsea’s other front six players, also capped a fine individual performance with his first Premier League goal of the campaign late on.