The Hornets were not at their best in securing a third straight league win for the first time in a year - and a third consecutive clean sheet for the first time since October 2007 - but the fact his side are now able to grind out wins will encourage manager Brendan Rodgers.
His opposite number, Neil Warnock, has other problems though. This was Palace's fifth defeat in seven games, although his complaints about the Hornets' opening goal after 22 minutes seemed to have some justification to it.
Don Cowie, a January transfer window acquisition from Inverness Caledonian Thistle, looked certain to be flagged offside when he raced onto Grzegorz Rasiak's flick and through a square and statuesque Palace defence.
But the decision never came and the midfielder admirably kept his composure to slide the ball beneath Julian Speroni and score his first goal for his new club.
The Palace manager's response was to vent his fury at Grant Hegley and Warnock only began to calm down after he had received a stern lecture from the referee.
Three minutes before the goal though, Alan Lee looked odds-on to give the visitors the lead when he was put through on goal, but was stopped by a fantastic sliding challenge from Adrian Mariappa.
But that was as close as the visitors got to equalising and Palace old boy Jobi McAnuff and Cowie both forced Speroni into sharp saves before the Hornets made the points safe with 19 minutes remaining.
Again Cowie was instrumental; on this occasion beating Nathaniel Clyne and getting to the by-line before driving the ball into the near post.
McAnuff got across Speroni, but the last touch was inadvertently applied by Eagles defender Jose Fonte.