The Bundesliga giants confirmed the 21-year-old shot-stopper would wear the number 20 shirt this season as he met the local press alongside new signings Lukasz Piszczek and Robert Lewandowski.

Dortmund boss Juergen Klopp admitted during the conference Langerak will be Dortmund number one Roman Weidenfeller's understudy this season.

Speaking to the Ruhr Nachrichten the ex-Melbourne stopper admitted the Bundesliga was a big step-up and said his main goal for his first campaign in Europe was to learn as much as possible.

"I hope to develop a healthy relationship with Roman," said Langerak who is still learning the basics of the German language.

Langerak claimed when he was told of Dortmund's interest he thought it was a bad joke, but was delighted to have made his way to Germany.

"In Australia, all soccer players dream of the clubs in Europe, from the Bundesliga," he said. "I really wanted to be there.

"Dortmund has a big name, a big tradition. The fact that this team wanted to have me, was like a present for me."

Langerak, who impressed as Melbourne's number one last season, made the switch to Dortmund after the German giants reached agreement with the Victory in May.

Borussia Dortmund sports director Michael Zorc added: "The things we saw of him convinced us."