The Baggies were one of the form teams in the division heading into their clash against a struggling Canaries, having won three of their last five games.
However, they looked extremely off the pace and it was Alex Neil’s men who took the lead early in the second half.
The first 45 minutes was a drab affair, before Robbie Brady netted after 50 minutes in what was the only shot on target in the entire game.
West Brom never troubled John Ruddy and Pulis bemoaned his side’s performance, considering they have been performing so well during the last month.
The Welshman said: “We have played so well over the last month or so, to put in a performance like that is really disappointing.
“We didn’t do anything but I don’t think they did anything. I said at half-time, sometimes you have to grind results out and it just seemed one of those games.
“Their goal was such a poor goal. They have had a break with it but it should never have got to where it got to.”
The victory moved Norwich three points clear of the relegation places, while the loss prevented West Brom from reaching the 40-point mark.