Langerak passed a medical on Monday and signed a three-year contract that will take him up to the 2018 FIFA World Cup in Russia.
Langerak made 27 appearances for Dortmund in five seasons at the Signal Iduna Park after leaving Melbourne Victory in 2010 but was foiled in his attempt to play more regularly by the consistency of veteran Roman Weidenfeller.
Stuttgart announced the capture of the Socceroos' number 2 on its website and on Twitter.
The six-times Socceroos stopper is the second goalkeeper to arrive at Stuttgart in a matter of days, with Poland's Przemyslaw Tyton having joined from PSV last week - and both were put their paces at a fun day training at Stuttgart.
Both will now be fighting it out for the number one jersey with new Stuttgart coach Alexander Zorniger saying his mind has yet to be made up.
"Langerak and Tyton are both very positive guys and we had to create this competition for a place in goal," Zorniger said at his first press conference in charge on Monday.
"We've got two players for this position who can fulfil our expectations."
Dortmund, now coached by Thomas Tuchel, signed Roman Burki from Freiburg this month to compete with Weidenfeller.
Langerak's failure to nail down a regular spot in the Dortmund team is seen as the reason he was unable to seriously challenge for the number 1 spot in the Australia national team.
That role is taken up by Mat Ryan, who plays regularly for FC Brugge and has been named goalkpeer of the year in in Belgium's top flight the past two campaigns.
