The former 1. FSV Mainz 05 defender, who has been training with the Westphalians for the past few weeks, is now officially part of Jürgen Klopp's first-team squad and, as such, eligible to make his debut against FC Bayern München at the weekend.
"We are reacting to the injuries in our defence," said Dortmund's sports director Michael Zorc. "Manuel Friedrich has a great deal of experience and he's made a very good impression in training."
Friedrich has already totalled 247 Bundesliga appearances, many under the guidance of Klopp from their time together at Mainz between 2004 and 2007. His last club was Bayer 04 Leverkusen, for whom he featured until his contract expired in the summer. He has been without a club since, but is now delighted to have been given another chance to play in the Bundesliga, not least for such a prestigious club.
Cover for Hummels
"I'm totally looking forward to being able to play at the Signal Iduna Park in a Borussia Dortmund shirt," said the 34-year-old. "I've only had that pleasure as a guest up to now, but to have the Gelbe Wand behind you and not against you has got to be an incredible feeling. I'm really looking forward to my time here."
Dortmund were struck by bad news earlier on Wednesday when it was confirmed that Mats Hummels and Marcel Schmelzer had both been ruled out of Saturday's table-topping encounter, as well as next week's UEFA Champions League tie with SSC Napoli due to injury.