After a frenetic opening period, when the ball spent more time in the air than on the ground, Watford almost took the lead with their first attack a Neil Cox cross was knocked down by Helguson to Allan Nielsen who pulled his shot wide.
Although the Hornets had started slowly their increasing pressure finally told on 39 minutes when Helguson nodded home what proved to be the winning goal.
Nielsen picked the ball up 40 yards out and hit a speculative shot which Brighton keeper Michel Kuipers could only palm into the path of the Icelandic international who had the easiest of jobs to head home from five yards.
Helguson almost extended the lead on 54 minutes with an ambitious half volley from 25 yards which drifted wide of the right hand post, before Brighton's Bobby Zamora should have leveled the scores.
After a mix-up in the Watford defence Zamora turned inside Paul Robinson but could only blast the ball straight at Alec Chamberlain from inside the six yard box.
As the match wore on Watford dominated and although Danny Webber missed a number of clear opportunities and Brighton's Kerry Mayo produced a brilliant last gasp blocking tackle from Nielsen's goal bound effort the Hornets comfortably held on to the three points.