Tommy Smith struck once in each half to cancel out goals from Lee Martin and Robert Earnshaw for the Reds.
But Tyson came off the bench to snatch the points for Colin Calderwood's newly-promoted side.
It took ten minutes for Forest to take the lead, in spectacular fashion, as Martin, the on-loan winger from Manchester United, showed a touch of Premier League quality as he bent an unstoppable 20-yard shot high into the corner of the net.
Forest could have doubled their lead when a Julian Bennett drive took a wicked deflection that steered it into the sidenetting.
Then a slip from defender Mathew Sadler allowed Chris Cohen to burst into the penalty area, only to power a shot straight at keeper Mart Poom.
Earnshaw turned deftly on the edge of the box before curling inches wide of the angle of post and bar.
And the missed chances looked costly when Watford equalised from a corner, with Paul Smith saving superbly to thwart an improvised effort from Leigh Bromby, only for Tommy Smith to sweep home the loose ball at the far post in the 23rd minute.
Forest regained the lead through Earnshaw, who chipped deftly over the advancing Poom after Guy Moussi's incisive pass had sent him clear in the 35th minute.
The second half began with Martin twice firing over during an intense spell of Forest pressure, while Gregorz Rasiak spurned a good opportunity at the other end.
It was a sign of Forest's dominance that Watford had used all their substitutes by the 59th minute, in an attempt to get back into the game.
And they did exactly that two minutes later, as Lloyd Doyley fired a low ball across the face of goal to the far post, where Smith sidefooted home the equaliser.
But Forest had an ace up their sleeves themselves, in the form of substitute Tyson, who put Forest ahead for the third time, slotting home from close range in the 67th minute after an Earnshaw free-kick had bounced back off an upright.
A swift break from Tyson then carved out another chance for Earnshaw, who again lifted the ball over Poom as he raced from his line, but this time saw his shot drop wide.
Tyson himself fired wide in injury time, as Forest looked to extend their advantage.