Leandra Little nodded in the first within ten minutes, beating Watford keeper Frances Kitching at the near post after Jess Sigsworth knocked the ball in from the left.
Belles grabbed another just before half time as, ollowing confusion from a throw in, the ball broke to Sigsworth who buried it from close range.
Watford hit the bar late on but failed to really test the keeper and stay at the bottom of the table.
A dominant display from Belles in the first half meant Watford only managed two attempts on goal from Helen Ward and Cherrelle Albert.
Home keeper Kitching pulled off a fantastic save to keep out Samantha Tierney, tipping the ball over the bar on the 70-minute mark.
Sigsworth and Kirsty Hanson also came close with further shots. Watford thought they had a goal back as an effort struck the bar and bounced directly down, but the referee didn’t give it and the Belles retained their two-goal margin.
Belles striker Sigsworth said:“It was a really tough game, I feel like as soon as we got the first goal it was good but to be fair to Watford they made it hard for us.
“But we battled it out, our main aim was not to concede and score goals and that’s what we did so it was great.
“They came at us in the second half but all we needed to do was stick to our game plan, stay nice and compact and work for each other and encourage each other.
“I think that worked and we kept them at bay quite well.
“It’s been great under the new manager, we all respect Neil a lot, it’s a great appointment for us.
“We’re playing well and training well under him so we’re excited to see what will come of it.”
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