Jordan Ibe gave the Rams a deserved lead at the interval with a superb curling effort and Bryson secured another victory for the Rams with a fine long-range finish, after Gianni Munari had equalised midway through the second half.
Derby started positively and almost took a fifth minute lead when Hornets goalkeeper Jonathan Bond made a fine save to deflect a Jeff Hendrick shot onto the post.
The visitors went on to dominate the opening 20 minutes in terms of possession and territory, but apart from a couple of blocked Ibe efforts, created little in the way of attempts on goal.
Watford’s only chance in that period came when Odion Ighalo let a Keith Andrews pass run through to Lloyd Dyer in the penalty area – but his shot lacked the power to really test goalkeeper Jack Butland.
The on-loan Stoke City stopper was tested in the 25th minute when he had to dive smartly to his right to keep out a Troy Deeney snapshot from the edge of the 18-yard box. The keeper also had to deal with Fernando Forestieri’s shot from outside the area soon after.
Forestieri who spurned a great chance to give the hosts the lead shortly before the half-hour when he was picked out unmarked in the penalty area by a Deeney pass – but he wanted far too much time to get his shot away, allowing Craig Forsyth to get back and concede a corner.
The next opening fell Derby’s way as Chris Martin showed superb skill to bring the ball down and burst away from Joel Ekstrand before hitting a low shot which Bond managed to push behind.
But the goal Derby had been threatening arrived in superb style in the 39th minute when Ibe stepped inside Forestieri on the left side of the penalty area before curling a superb shot across Bond and into the far corner.
But for the Hornets keeper’s acrobatic tip over, Martin would have made it 2-0 soon after with a header after being picked out by a well-flighted Omar Mascarell free-kick.
Lifted by the inclusion of top scorer Matej Vydra at the start of the second half, Watford improved. They had more of the ball and offered a greater attacking threat after the break.
Forestieri went close with a couple of long-range efforts before the Hornets equalised in the 68th minute when some fine build-up play down the left ended up with substitute Munari being put through on goal – and he fired high past Butland.
Having levelled, Vydra almost put his side in front moments later with a rasping drive that flew inches wide. But Derby still had more to give going forward and after Bond had once again excelled to deny Martin from close range, they regained the lead with a superb long-range strike from replacement Bryson in the 81st minute.
The Rams needed Butland to come to the fore twice to preserve their advantage though. First, he made an instinctive save to divert a Munari shot over his own bar, before also diverting an Ikechi Anya shot behind for another corner.