The Baggies secured their third win of the season as an own goal from Esteban Cambiasso early in the second half proved to be the difference between the teams.
Irvine believes that his side will take a great deal of confidence from their display heading into an important run of fixtures.
He told BBC Sport: "It means a lot. It is a difficult place to come to and we are the first team to win here. We had to cope with the pressure they put you under and we had to pass the ball. I'm really pleased with the performance.
"It was a complete team performance. We needed a threat up front and we did that. At the back we were solid against some really difficult forwards to play against. Three points. Clean sheet. It's a great feeling for us and it gives us a platform to go into the next game - Newcastle at home - which will be really difficult for us.
"I said all along it was going to take a bit of time, but it was important to find the best way of playing for our group of players and we are getting closer to that."
West Brom are 10th in the Premier League table following their win over the Foxes.