First-half counter-attacking goals from Tamas Priskin and Tommy Smith did the damage, but the manner in which Brendan Rodgers' side controlled proceedings thereafter suggests they will have few problems in preserving their Championship status.
The visitors dominated the early exchanges and looked set to extend their fine run, but after Thomas Butler and Joe Allen had tested keeper Scott Loach, they found themselves behind after 23 minutes.
The excellent Lloyd Doyley started the move off by winning back possession and finding Jobi McAnuff, who in turn laid a fine ball towards the right side of the penalty area where Tommy Smith had found space.
The Hornets' leading scorer wasted no time in laying a low ball back across the penalty area for Priskin, who had surprised Chelsea with the opening goal in Saturday's FA Cup tie, to apply the finish from six yards.
The creator of Watford's opener then turned scorer nine minutes later, but only after assisting in the move that almost set up a goal on his full debut for new signing Dan Cowie.
Smith released McAnuff in the inside left channel and, after getting to the byline, he pulled the ball back to the former Inverness Caledonian Thistle midfielder, who looked certain to score, only for Dorus de Vries to pull off a fine save.
However, the ball was then hooked clear to the edge of the area where Smith struck a first-time right-footed shot inside the keeper's post to register his 13th of the season.
Smith and Lee Williamson could have extended Watford 's advantage after the break, as the visitors rarely looked like seriously threatening Loach's goal, despite their best, but limited, efforts to get back into the contest.