Watford dominated the early proceedings in what was Quique Sánchez Flores' last game in charge of the Hornets with good chances from Almen Abdi and Nathan Aki, but a late goal from Jack Rodwell and a wrongly disallowed effort from Duncan Watmore saw the Black Cats end the half strongly.
Watford produced an instant reply in the second half with Sebastian Prodl's equaliser which was instantly canceled out with Jeremain Lens restoring the visitors lead before Deeney sealed the draw from the spot on the hour mark.
End on a high
Flores was looking to finish his tenure at Vicarage Road on a high and had three opportunities to take the lead in the opening 35 minutes.
The first came just five minutes into the contest as Abdi turned well on the edge of the Sunderland and despite having skipper Deeney in support he decided to go for goal and it was just wide of Jordan Pickford's post.
That was followed up by Jose Manuel Jurado who looked to try one from a similar position to Abdi and Pickford made sure it wasn't going to beat by tipping it over the crossbar.
Chelsea loanee Ake had impressed during his time on the outskirts of the capital and he let one rip as the ball trickled into his path but Pickford was there again to plam it away.
Against the run of play
Sunderland had managed to complete their survival mission earlier in the week and it did show in their performance early on but somehow managed to take the lead with their first significant opportunity.
Youngster Rees Greenwood did well to play the ball out to Lens whose excellent ball across the face of goal was just too much for Watmore but it was perfect for Rodwell who simply tapped home at the post.
It should have been two as Dame N'Doye played the ball through to Watmore who coolly slotted past Heurelho Gomes but the flag on the far side was wrongfully raised for offside.
Watford had an instant reply as they equalised moments after the restart and it was simple enough as Prodl hammered home the header into the roof of the net.
Sunderland seemed to have the attitude anything that their hosts could do, they could do better as they managed to regain their lead almost instantly.
It was great counter-attack from Allardyce's side led by Watmore who plays in Lens. The Dutchman has struggled in his debut season on Wearside but showed what he could do as he sent Ake on his backside before sliding it under Gomes.
Allardyce's were denied another goal by the flag of the assistant as Sebastain Larsson's free-kick found the head of N'Doye who slid it home with the header but once again the flag was raised.
The Black Cats had been on the end of some questionable decisions from referee Kevin Friend and his assistants and there proved to be one more left as the home side were handed a spot kick on the hour mark.
It looked a seemingly harmless challenge from John O'Shea as he bundled over Jurado but Friend pointed to the spot and Deeney made no mistake sending Pickford the wrong way.