The game was finely poised between the two London teams before Hazard burst clear, set on his way by Mateo Kovacic and he showed composure to round Watford goalkeeper Ben Foster to reach his century in a Chelsea shirt.
Goal No 101 swiftly followed from the penalty spot as he propelled his season tally into double figures with his brace ensuring Roberto Pereyra's strike was nothing more than a consolation. A breakdown by competition shows Hazard has scored 79 times in the Premier League, 10 in Europe and 12 in domestic cup competitions.
Hazard continues to be a model of consistency for the Stamford Bridge club despite the chopping and changing of managers.
This season under Maurizio Sarri, the 27-year-old has been directly involved in 19 goals in the league this season (10 goals, nine assists); the most of any player in the competition.
Speaking to Sky Sports, Hazard said: '(The 101 goals) mean a lot especially because we won today.
'One-hundred-and-one goals with this amazing club is something I will never forget!'Now I think me, the fans and players want more. I want to score more goals for the club and want to be a legend like (Frank) Lampard, (Didier) Drogba and try to be my best. 'My target is to score goals and try to win the game. I try to do my best and today I did well.'
His first goal for the club came at Stamford Bridge on August 25, 2012, against Newcastle United.
Hazard scored from the penalty spot before Fernando Torres wrapped up a 2-0 win. The Belgian has not looked back since then.
It is no surprise to club bosses or supporters that he remains attractive to Real Madrid as he continues to take centre stage for Sarri's side in the race for a top-four spot.