Troy Deeney's ninth goal of the season earned a point for Watford, who had substitute Adrian Mariappa sent off.
Hull started superbly when Andy Dawson's fine cross from the right was headed in by James Chester.
But the Hornets soon levelled when John Eustace slipped the ball inside on the left edge of the penalty area and Deeney turned it home from six yards.
Hull's Corry Evans hit the bar and Mariappa, who came on at half-time, saw red for two bookings in four minutes.
The point did little for either side, both of whom remain some way from the play-off places.
Following the two early goals, Watford goalkeeper Tomas Kuszczak, on loan from Manchester United, kept out Chester's header from a Dawson corner and also blocked a Matty Fryatt strike.
Evans saw an angled drive from inside the area strike the woodwork, while Josh King was narrowly off target with a header from Robert Koren's cross.
Watford defender Carl Dickinson twice went close to putting his side in front with a header and then a shot wide in as many minutes.
Hull sensed victory but Koren fired just wide from the edge of the area and then had a shot blocked.
Hornets manager Sean Dyche sent on Chris Iwelumo with seven minutes remaining and within 60 seconds the striker lashed a low shot inches wide, but the game ended in stalemate.
Watford 35 Kuszczak 03 Dickinson 05 Taylor (Mariappa - 46' Dismissed after an earlier booking ) 12 Doyley 33 Nosworthy 04 Eustace 19 Buaben 22 Murray 32 Hogg 09 Deeney 25 Garner (Iwelumo - 83' ) Substitutes 01 Loach 06 Mariappa 24 Whichelow 26 Assombalonga 10 Iwelumo Hull 28 Mannone 02 Rosenior 03 Dawson 05 Chester Booked 34 Cooper 08 Evans 10 Koren 14 Cairney 12 Fryatt 27 King (Stewart - 52' ) 29 Garcia (Brady - 75' ) Substitutes 13 Oxley 26 Bradley 07 Stewart 30 Olofinjana 17 Brady