Match ends, Watford 3, Blackburn Rovers 3.
An injury-time header from Rudy Gestede secured a point for Blackburn at Vicarage Road, denying Watford a seventh straight home win.
Marco Cassetti's volley put Watford ahead but David Dunn equalised, before teeing up Craig Conway who calmly finished from eight yards.
Watford were level when Troy Deeney scored a penalty and took the lead through substitute Cristian Battocchio.
But there was late drama as Tommy Spurr's cross was met by Gestede.
Both sides look set for another season in the Championship, locked in mid-table with nine fixtures remaining, but the Hornets' fine home form had given their fans some hope of a repeat of last year's run to the play-off final.
They led when Cassetti buried his first goal for the club from Deeney's cross, but Dunn lashed in from the edge of the box after Manuel Almunia had punched out a corner.
Veteran Dunn then slid in Conway for Rovers' second, only for referee Darren Sheldrake to penalise Todd Kane for handball, with Deeney scoring the penalty.
Battocchio ran clear to score with two minutes left but there was still time for Gestede to head in a last-gasp leveller.
Blackburn boss Gary Bowyer:
"We were comfortable at 2-1 and the penalty changes the course of the game.
"Our lad is stood two yards from (Ikechi) Anya when he crosses it and the ball hits the hand.
"We need to clarify, for the sake of the game, what is handball in the penalty area because you guys, you report on it and one week it's not been given and one week it has been given.
"We need some clarification because it changed the course of the game."
Watford head coach Beppe Sannino:
"I'm very disappointed but in English football you have to pay attention to the last, last minute of the game. This is the rule of English football.
"We nearly won this game but it was not only this game. Since I joined the club there were many games we have dropped points in the last five minutes of games.
"This game reflects Watford's season perfectly."
- 4AngellaBooked at 76mins
- 31HobanSubstituted forMcGuganat 72'minutes
- 8MerkelSubstituted forDiakitéat 75'minutes
- 16MurraySubstituted forBattocchioat 61'minutes
- 2KaneBooked at 85mins
- 4KilgallonBooked at 90mins
- 29EvansBooked at 78mins
- 8DunnSubstituted forVarneyat 90'minutes
- Darren Sheldrake
- Shots on Target
Second Half ends, Watford 3, Blackburn Rovers 3.
Corner, Watford. Conceded by Corry Evans.
Attempt blocked. Luke Varney (Blackburn Rovers) right footed shot from the centre of the box is blocked. Assisted by Rudy Gestede with a headed pass.
Attempt missed. Marco Cassetti (Watford) header from the centre of the box is close, but misses to the left. Assisted by Daniel Tözsér with a cross following a corner.
Corner, Watford. Conceded by Todd Kane.
Goal! Watford 3, Blackburn Rovers 3. Rudy Gestede (Blackburn Rovers) header from the centre of the box to the bottom right corner. Assisted by Matthew Kilgallon.
Luke Varney (Blackburn Rovers) wins a free kick in the defensive half.
Foul by Daniel Tözsér (Watford).
Matthew Kilgallon (Blackburn Rovers) is shown the yellow card for a bad foul.
Foul by Matthew Kilgallon (Blackburn Rovers).
Troy Deeney (Watford) wins a free kick on the right wing.
Substitution, Blackburn Rovers. Luke Varney replaces David Dunn.
Goal! Watford 3, Blackburn Rovers 2. Cristian Battocchio (Watford) right footed shot from the centre of the box to the bottom right corner. Assisted by Ikechi Anya following a fast break.
Foul by Gabriele Angella (Watford).
Jordan Rhodes (Blackburn Rovers) wins a free kick in the defensive half.
Todd Kane (Blackburn Rovers) is shown the yellow card for a bad foul.
Lewis McGugan (Watford) wins a free kick in the defensive half.
Foul by Todd Kane (Blackburn Rovers).
Attempt missed. Rudy Gestede (Blackburn Rovers) header from the centre of the box misses to the left. Assisted by Paul Robinson following a set piece situation.