Wagner's side thoroughly deserved the win as they dominated for large periods and were very clinical in front of goal. Alex Pritchard had given the hosts the lead early on with his first goal for the club but Junior Stanislas quickly levelled things up. However, this was not enough to send the away side into the break on level terms as Steve Mounie headed the hosts back in front.
The Terriers punished Bournemouth further in the second-half as Mounie grabbed his second goal of the game and Rajiv van La Parra converted from the penalty spot in injury time to add gloss to the scoreline.
Wagner was delighted with the result considering the Terriers had to play 120 minutes against Championship side Birmingham City in the FA Cup on Tuesday night and because of the run of form Bournemouth were on ahead of this game.
He said: "This makes the performance which was a very good one, even bigger from my point of view. We were defensively very organised, aggressive, focussed and we created dangerous situations. We scored four wonderful goals."
He added: "We minimised (Bournemouth's attacking threat) this today because all the players worked together. We have seen some fantastic individual performances."
A number of impressive performances
The crowd at the John Smith's Stadium got their first proper look at new signing Pritchard in today's game and he impressed throughout. The 24-year-old looked a constant threat in midfield and grabbed his first goal for the club in the first-half with a neat finish.
Wagner was pleased with his performance. He said: "He was a handful today. He scored, he got an assist, he always wanted to have the ball, in tight spaces he was creative, his link-up play was very well, he played fantastic. This is why we signed him. He will help us and he showed today what a great player he is."
23-year-old striker Mounie also impressed again as he took his tally for the season to six with his third brace of the campaign. Wagner hailed his outstanding performance.
He said: "His link-up play was very good. It was an outstanding performance from Steve Mounie. He did not score his hat-trick because Rajiv van La Parra had an idea, a good one to be honest. I am happy for Rajiv that he scored this penalty."
However, the standout performer for the Terriers throughout this game was midfielder Aaron Mooy who has been instrumental for Wagner's side this season. His exceptional delivery caused Bournemouth huge issues all afternoon but his game was cut short as he was stretchered off through injury.
Wagner revealed that his injury is not as bad as it looked as he has not suffered any ligament damage. He said: "We have to wait. He has a cut on his knee and has got some stitches. We have to see how quick he can cover."
The Terriers had not picked up a single point in 2018 heading into this game and Wagner recognised the importance of picking up a win in this afternoon's match and now believes his side are building momentum.
He said: "We said this in the preparation to the game. Now it is time not only to believe but to fight for it. Not only the players, the whole town has to fight for it. This is what everybody has to show and I think the supporters have shown it today."
He added: "This is a massive game for us but in the dressing room at Old Trafford, we said we have the difficult fixtures behind us and now it is time to start to build momentum. It is one thing to speak about it and it is another to do it."
With Manchester United travelling to Yorkshire this weekend to take on the Terriers in the FA Cup fifth round, Wagner is hoping his side can maintain their momentum for as long as possible.
He said: "We would like to keep it as long as we can. I am very confident and I have the belief that we have a chance to survive. We will work as hard as we can to take this chance."