United secured only their third clean sheet of the season by keeping a defensive-minded Palace at bay in a contest that was settled by Juan Mata's 67th-minute strike.
Van Gaal was pleased with his side's discipline at the back, although he still feels they have improvements to make in that area.
"It's not a matter of defence, it's a matter of organisation when we don't have the ball," the Dutchman said.
"It is the whole team who have to defend. Today we were better in that shape but, in spite of that, one minute before half-time there was a misunderstanding between [Paddy] McNair and [Daley] Blind and it could be 0-1 and maybe I sit here differently."
The Dutchman was still satisfied by United's display, which put them two points adrift of the top four ahead of the trip to Arsenal after the upcoming international break.
"They [Palace] came here to defend. We played the first half reasonably well. We had patience, we played the ball but I think 'Okay, we need more speed and more switches'," the Dutchman added.
"But we had a lot of time on the ball, we created possibilities. We could have scored in the first half but I said at half-time 'Okay, I think we [are playing] better than the matches before because we keep the patience more and the opponents shall tire'.
"After the [goal], we have created more big chances because they have to come [and attack] and then we have created the chances.
"I'm happy. We have three points and we are staying two points behind fourth. It's in our hands and that's important."
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