The forward, on Tuesday, signed a three-year deal with 1. FC Union Berlin and leaves Rennais after just one goal in his time there.
No transfer fee has been made official by either club, with both sides agreeing to stay silent on the matter.
Struggle for form outside Austria
The last two seasons have been incredibly forgettable for Hosiner, who has struggled to find the form that made him a target for plenty of teams around Europe.
28 games, two goals. That's how the Austrian's record reads over the past stints with Köln and Stade Rennais, a far cry from how good he was in his homeland.
During his time with Austria Wien, domestically, Hosnier found the net 41 times in 64 games and added a further 15 assists in that time.
The now 27-year-old also enjoyed a stint in Germany with 1860 Munich and SV Sandhausen. He failed to make a first time appearance for the Lions, scoring once for SVS.
Hosnier has his say
Upon confirmation of the transfer, the forward spoke to the Union club website to give his reaction on the move.
He explained, "I am relieved and happy that the transfer has finally worked out and I am looking forward to the new challenges at 1. FC Union Berlin."
Hosnier added, "The talks with the Union board quickly convinced me, so it has been clear for a long time that I wanted to make this move."
He concluded, "I am now glad that I can complete the entire pre-season with my new team to successfully start the season."