A composed finish by the Championship's leading goal scorer, Marlon King has Watford in front at Selhurst Park.
After an even opening the Golden Boys gradually got on top and King finished with aplomb on 28 minutes after defeating the Palace off side trap. Picking up a through pass from captain, Gavin Mahon King raced from the half way line before rounding Palace custodian, Gabor Kiraly and slotting home for his 19th goal of the campaign.
The hosts' Clinton Morrison nearly leveled for the South Londoners soon after but keeper, Ben Foster made a fine save low to his right.
Andrew Johnson had appeals for a penalty turned down as half time approached, but it is Watford who has the advantage at half time.