Andre Gray and Danny Welbeck had chances to hand the Hornets their first three points of the campaign, but the former was guilty of missing an open goal, while Welbeck's second-half effort was thwarted by Blades' goalkeeper Dean Henderson. Craig Dawson's header was then brilliantly saved by Henderson in stoppage time.
On an afternoon lacking in quality, there was one positive for Watford as they secured their first clean sheet in the Premier League since a 1-0 victory against Everton here 238 days ago – a run of 20 matches.
Watford remain rooted to the foot of the table as Sheffield United move on to nine points from their opening eight matches.
Quique Sanchez Flores was brought back to Vicarage Road with the assignment of patching up one of the league's leakiest defences.
And the Spaniard signalled his intent with a flat back five as Sebastian Prodl was handed his first league appearance of the campaign.
The Hornets started the afternoon as the only team in the top flight yet to register a win, and they began the opening period like an outfit devoid of confidence.
Watford's defensive-minded side allowed the Blades to take control, but with nine minutes gone, it was the hosts who spurned a fine chance to take an unwarranted lead.
Following confusion amongst the United backline, Roberto Pereyra found himself in space on the right-hand side. He played in Gray, but the former Burnley man blazed over from underneath Henderson's crossbar when it appeared easier to score.
Gray's missed chance would be Watford's best opportunity of a turgid 45 minutes. Indeed, the home side had Ben Foster to thank for tipping Craig Cathcart's attempt at a clearance over the woodwork midway through the first half.
The Blades, who have enjoyed an encouraging return to the top flight, had greater possession than their hosts, but – bar a John Fleck shot which was smothered by Foster – created little to show for it.
Referee Andre Marriner put Vicarage Road out of its misery by blowing his whistle on the stroke of 45 minutes, and not one second more.
Sheffield United returned from the interval before their hosts, but they were caught cold after 49 minutes when Welbeck had the chance to score his first Premier League goal for Watford and his first in the top flight since the opening day of last season.
The former Manchester United and Arsenal forward, whose career has been plagued by injuries, showed he has not lost his pace by leaving the Blades' defence trailing as he charged down on Henderson's goal.
Welbeck had Gray to his left, but the 28-year-old went for glory only for the on-rushing Henderson to block his effort. Gray was quick to vent his frustration.
Flores and opposite number Chris Wilder made several changes, but the second-half fizzled out with perhaps both managers happy to take the point.
In injury time, second-half substitute Gerard Deulofeu's free-kick fell to Dawson, but his header was stopped by a diving Henderson.
It would prove virtually the last action of the game as a chorus of boos greeted the final whistle.