The Blues squandered a two-goal lead in the second half but battled back late on through a Cesc Fabregas winner, earning them a record-equalling 29th top-flight win of the season.
For all Watford's efforts they were unable to end their miserable run of form, which now stands at five defeats in a row to leave them down in 16th place with one game remaining.
Among those to come in for just a fourth league start of the season was skipper John Terry, who marked what will likely be his penultimate appearance at Stamford Bridge with his 67th goal for the club.
After an uneventful opening quarter to the match, Terry reacted quickest to prod home from an uncleared corner to finally spark the game into life.
Watford, previously without a goal in any of their last five away outings, responded almost immediately through Etienne Capoue, who capitalised on a poor defensive header from Terry to nod past stand-in keeper Asmir Begovic.
A relatively quiet Eden Hazard had a chance to edge his side back ahead 34 minutes in, cutting inside into a good position but seeing his shot take a touch on its way wide of the target.
It did not take Chelsea too much longer to regain their advantage, however, as another unlikely scorer in Cesar Azpilicueta found a way through, picking out the bottom corner with a half-volley inside the box to open his own account for the season.
The scoreline remained that way at the break - bad news for the visitors, as they had failed to recover from a losing position at the midway point to win a match in 55 Premier League attempts.
Much like in the first half, though, Watford were back into the contest instantly after Daryl Janmaat took matters into his own hands, jinking past a couple of players and keeping his composure when up against Begovic.
Only twice before had Chelsea shipped more than once on home soil - in defeats to Liverpool and Crystal Palace - but they were in no mood to gift the Hornets a share of the spoils in the remaining 40 minutes or so.
Batshuayi had a shot kept out by Gomes and Azpilicueta was also denied by the Brazilian at full stretch, yet it was the visiting side who found the sixth goal of the evening.
Three minutes after being brought off the bench, Stefano Okaka - capped for the Italy national squad by Conte - profited on some more slack play at the back to slam home following a scramble.
Substitute Ola Aina and Janmaat both came close to finding a way through before the killer seventh did arrive, with Fabregas tucking past Gomes from the edge of the box after being picked out by Willian.
Watford failed to muster one last response in the final few minutes, and their night turned sour when Sebastian Prodl was shown a second yellow at the death for a trip on Pedro as things threatened to boil over at the end of a lively contest.