Chalobah and Troy Deeney earned the Hornets back-to-back victories in the npower Championship for the first time this season, following on from last weekend's 6-1 rout at Leeds.
Hornets boss Gianfranco Zola said: "It was good. Although they were playing with 10 men, we created a lot of chances and we had good opportunities.
"It is fair to say they put a lot of pressure on, especially in the last 10 minutes, but we certainly played a good game and there were spells in the game when we played very good football. Nobody can say it wasn't a deserved win."