Watford lead Brentford at half time in their Championship clash thanks to Odion Ighalo's late goal.
Billy McKinlay, who is taking charge of Watford for the first time, saw Ighalo's header from Lloyd Dyer's cross hit the woodwork for the hosts midway through the first half.
However, his side took the lead through Ighalo just before the break after the striker was felled inside the Brentford box.
Ighalo saw his penalty saved by David Button, but reacted quickest to convert the rebound.