Ipswich lost for the seventh game in a row as Watford came from a goal down to win at Portman Road.
Things were looking good for the home side when Keith Andrews headed them in front from Daryl Murphy's cross.
However, Marvin Sordell levelled the scores from the penalty spot after he was fouled by Ibrahima Sonko.
And Troy Deeney secured the win for the Hornets from close range to leave Town winless since 18 October and on their worst run since the 1994/95 season.
Town now sit just one place above the relegation zone and only kept out of the bottom three courtesy of a superior goal difference to 22nd-placed Nottingham Forest.
In contrast, Watford have now gone four games unbeaten as they look to steer themselves away from the drop zone. They are now 17th, four points better off than their opponents.
Town could, and probably should have conceded the first goal but Sordell blazed a great chance over in the 12th minute.
The decisive moment of an uneventful first half came right at the end when Murphy's cross was converted at close range by the head of Andrews.
The second half was more open with Jason Scotland failing to get on the end of a Lee Martin cross and Aaron Cresswell's set-piece well parried by Watford keeper Scott Loach.
A goal was there for the taking and it was the visitors who claimed it in the 70th minute as Sordell made no mistake from the penalty spot after he himself was fouled by Sonko.
Four minutes later, Watford struck the killer blow as Martin dallied on the ball in defence, allowing Deeney to capitalise and finish.