Ahmet Brkovic's first goal of 2006, 17 minutes from time, rescued a point for Luton at Vicarage Road to virtually end Watford's hopes of automatic promotion.
King volleys home the opener
Marlon King had opened the scoring with his 20th of the season when he latched onto Ashley Young's pass to lob home.
But Brkovic made amends for misses by Kevin Foley and Warren Feeney when he poked home Carlos Edwards' throw-in.
The draw leaves the Hornets nine points adrift of second-placed Sheffield United with four games to play.
It also means Luton's slim hopes of gaining a play-off spot were extinguished.
Watford manager Adrian Boothroyd
"If we do end up in the play-offs, the other teams will look around, and none of them will want to play us.
"I know this because we are a good team. We are still thinking about automatic promotion, because there are still plenty of tough fixtures coming up, and plenty of points to be won.
"We faced relegation last season, so to secure a play-off place is progress. But all we are thinking about is promotion."
Luton manager Mike Newell
"If the club has ambition, they will want to keep me, just as I will want to keep the players.
"I'm confident of keeping the squad together because most of them are still under contract, but I will have to have some backing from somewhere if we are to keep it that way.
"Anyway, I'm happy to get something from the game. If we had picked up more points on our travels, we could have been where Watford are, but I was pleased with the performance."
Watford: Foster, Doyley, Mackay, DeMerit, Stewart (Chambers 66), Eagles (Bangura 67), Mahon, Spring, Young, Henderson, King.
Subs Not Used: Chamberlain, Carlisle, McNamee.
Booked: Doyley, King.
Goals: King 36.
Luton: Beresford, Foley (Morgan 90), Davis (Barnett 17), Perrett, Heikkinen, Edwards, Robinson, Brkovic, Howard, Feeney (Vine 68), Showunmi.
Subs Not Used: Brill, Holmes.
Booked: Showunmi, Howard, Heikkinen.
Goals: Brkovic 73.
Ref: M Dean (Wirral).
The BBC is not responsible for the content of external internet sites