The 22-year-old will spend the rest of the season at the Coface Arena in a bid to build up more top-level experience after finding chances limited with Borussia DortmundBorussia Dortmund have confirmed that attacker Jonas Hofmann has joined Mainz on loan until the end of the season.
The 22-year-old joined BVB in 2011 from Hoffenheim and had steadily made inroads into Jurgen Klopp's first team over the last couple of seasons.
However, the return of Shinji Kagawa from Manchester United has left him surplus to requirements and he has moved to Coface Arena until June 2015.
"It is really important for me to get some match practice at an ambitious club," the Germany Under-21 international said.
"I'd like to thank Borussia Dortmund, the fans and all my team-mates. My love affair with Borussia Dortmund is far from over."
Sporting director Michael Zorc added: "Jonas Hofmann has huge potential for future development. We are convinced in Jonas' talent and we have both decided that it makes sense of him to get match practice at the highest level."