John Eustace and Danny Graham had Watford 2-0 up inside 24 minutes to silence a packed Carrow Road who were eager to see the Canaries carry on the momentum from their League One title win in May.
Norwich lost 7-1 at home on the opening day last season and while they improved after the break to score through Andrew Crofts, another poor start to the campaign was confirmed when Graham struck his second late on.
Michael Nelson was able to find a second goal for the hosts in stoppage time but Watford were worthy winners.
Norwich boss Paul Lambert handed debuts to six new signings and had captain Grant Holt on the bench despite a thigh injury and a possible court appearance in Shropshire hampering his build-up to the game.
Watford signed Troy Deeney from Walsall earlier in the afternoon and he was on the bench as boss Malky Mackay - who spent six years as a player for the Canaries - looked to engineer a win.
Watford captain Eustace had the first effort of the night - and the season - but blasted over from 25 yards before Simeon Jackson saw a shot blocked after a crisp passing move by the hosts.
The visitors were looking dangerous on the break and took the lead through Eustace in the 14th minute.
Don Cowie took a short corner and lofted the return pass into the penalty area.
Crofts misjudged his leap and Eustace was afforded the space to bring the ball down on his chest before planting a low left-footed shot past John Ruddy and into the corner.
Andrew Surman came close to an equaliser but his dipping free-kick was clawed out by Scott Loach - and Graham soon had the Hornets two ahead.
Lloyd Doyley hooked a clearance upfield and Graham cushioned the ball on his chest to strike partner Marvin Sordell.
Sordell helped the ball on over the top and Graham was lethal in clipping the ball past Ruddy from just inside the area.
Norwich were in need of a huge improvement if they were to find a way back and their best move of the night saw Crofts pull one back in the 52nd minute.
Wes Hoolahan slalomed his way past three players before finding Jackson on the edge of the area.
The Canada international had spotted Crofts run behind him and slid a lovely backheel into his path and the midfielder duly dispatched it past Loach.
Holt was summoned from the bench with 20 minutes remaining but Watford wrapped up the points through Graham's second goal in the 81st minute.
Stephen McGinn poked the ball through to Graham on the left-hand side of the box and the former Carlisle man picked his spot perfectly to curl home.
Nelson gave City hope in added time when he met Crofts' cut-back to steer in from 10 yards.