The fourth-placed Reds closed the gap between themselves and still-second Leeds to just a point, inflicting a fourth defeat on United in five Championship outings.
Forest's delighted head coach called it a 'massive' result and one they earned against a visiting side making an uncharacteristic number of errors.
"Massive result, massive performance, we deserved the victory and probably we can draw the game but we disturbed Leeds in the first half," he said.
"They made a lot more mistakes than usual, early and we were in a good position, we created a lot. I'm so proud and so happy for the players, they absolutely deserve these three points."
Lamouchi dubbed Leeds 'probably the best team in the league' and wants the same mentality he saw from his players in today's game, when they play again in midweek against Charlton Athletic.
"We are working together just seven months," he said.
"Last week I was really upset with them and today I loved them. This league is crazy, in three days we play again, we don't have time to be worried, to be happy, we need to be ready for the next fight. With this kind of performance against probably the best team in the league, we need to know why we disturbed them, why we won and why we can believe.
"My role is just to keep the same mentality. We need to play with the same commitment from everyone. Today my team was massive, played very well, especially first half. I don't remember one shot in the first half, for Leeds. It is not usual. This kind of team, with his quality, without [Kalvin] Phillips the team is a little different."
Although he said he didn't want to talk about Leeds, he did suggest they might be tired, as many sides are at this stage of a gruelling Championship season and offered suggestions on why his men got the better of Marcelo Bielsa's team, including the belief that Forest were more cohesive as a unit.
"Probably tired, in February many teams start to go down because this league is so difficult.
"I don't want to talk about Leeds. We played with a plan, we respected the plan. It was probably a bit lucky for the great save by [Bryce] Samba but we deserved to close the game before with [Lewis] Grabban. The goal was completely open and he shot at the keeper. The last minute with a small mistake we scored the second one.
"[There were] more mistakes from Leeds. The wingers didn't make the difference today, no fluidity between the lines. He made a change with [Ben] White in the middle and it was a little bit different. We changed [Joe] Lolley behind Grabban and it disturbed them a lot. We defended so well. We played as a team, more than the opponent tonight. We were more organised than them. Less mistakes.
"I don't know [if Leeds are tired]. I think so. Like all teams. I hope, because my team is tired. Watching some games, it is logical after 30 games. Boxing Day, no break, some players are more tired than others, some teams more than other teams."