King rammed home his 21st goal of the season to earn Watford a share of the spoils in the 65th minute.
He saw red 20 minutes later after blasting the linesman for not awarding a penalty when King felt he had been fouled by Joleon Lescott.
But, as far as Wolves were concerned, King had already done more than enough damage as his equaliser finally ended their slim hopes of clinching a place in the play-offs.
Wolves needed to win their final four games of the season to have any chance of joining Watford in the play-offs.
They looked on course to see off the Hornets when on-loan Arsenal striker Jeremie Aliadiere gave them a 17th-minute lead with his first goal at Molineux.
But some poor finishing, particularly by Tomasz Frankowski, cost them dearly as Watford earned a share of the spoils with a spirited second-half fight-back.
King, who turned down a move to Wolves from Nottingham Forest last summer in favour of joining Watford, saved Adrian Boothroyd's side from a third defeat in four games with his well taken strike.
Watford were fortunate to make it to half-time just trailing by one goal as they failed to create a real chance apart from the opening they were gifted by the sliced clearance of goalkeeper Stefan Postma in the eighth minute.
Postma's clearance flew straight to Darius Henderson but the Dutchman managed to scurry back to make the save.
Wolves were dominant in terms of attacking and made a deserved breakthrough when Aliadiere converted a superb cross-field pass from Frankowski.
It should have sparked an avalanche of Wolves goals but Colin Cameron shot wide, as did Lee Naylor who also had a free-kick well saved by Ben Foster in the 25th minute.
Foster saved Watford again six minutes before half-time.
Frankowski was released by Rohan Ricketts and only had Foster to beat, but the on-loan Manchester United 'keeper spread himself to deny the Poland international, who is still looking for his first goal for the club after his arrival from the Spanish side Elche in January.
It proved to be a costly miss and was fully exploited by Watford who raised their game a level in the second period.
King had a sighter in the 58th minute when he fired over the bar but he could not miss seven minutes later when he was unmarked on the far post to rifle home a cross from Matthew Spring.