Virgil van Dijk, Memphis Depay and Georginio Wijnaldum combined to give the Oranje a memorable 3-0 victory in Amsterdam on Saturday.
The result marked Netherlands' biggest ever win over Germany and took them to within a point of group leaders France.
It’s been a tough few years for the Dutch, who have gone through four managers in the last four years and failed to qualify for this summer’s World Cup in Russia.
They have struggled for any sort of consistency under Koeman, but Saturday’s performance was a lot more encouraging, with a number of the Oranje’s talented youngsters playing a significant part in their mauling of Joachim Low’s side.
Koeman, though, is not getting away by a third win in his seventh match in charge.
"Well I'm not going to glide across the dancefloor, but of course I'm proud. This is a great result," the ex-Everton manager said.
"We were waiting a long time for this, but I'm not the kind of guy who pretends that we've become world champions.
"I'm proud because finally we got the result we needed and we can say 'yes, there is development in the team'. That's what we needed. You could also feel that in the stadium, in the atmosphere.
"But if I tell the players that everything was great, it's not good. We need to grow with each other.
"I'm so happy for the guys, they've worked so hard for it."
The defeat piled the pressure on Germany manager Low, who has come in for plenty of criticism in the last few months after his side failed to make it past the group stages at the World Cup.
Netherlands meet Belgium in a friendly on Tuesday before their Nations League group-stage campaign wraps up in November.
They will, however, be without captain Van Dijk for their friendly with Roberto Martinez’s side, after the Liverpool defender withdrew from the squad because of an ongoing rib injury.