Lennart Thy is to return to Werder Bremen in the summer after turning down St Pauli's offer of a new contract.
The 24-year-old, who played for Bremen between 2007 and 2012 before moving to the second-tier club, will return on a free transfer when his current deal at St Pauli expires.
He has signed a three-year contract with Bremen.
"We are really pleased to have been able to convince Lennart Thy to return to Werder," said Bremen's general manager Thomas Eichin.
"He's a very interesting player who fits in perfectly here."
- SV Werder Bremen EN (@werderbremen_en) January 18, 2016
Pauli are sorry to lose a player who has scored 16 goals in 101 games for them, seven of them this season, of which four came in a 4-0 win over Fortuna Dusseldorf.
"We would have liked to have kept hold of Lennart, but of course we respect his decision," said the Hamburg-based club's general manager Thomas Meggle.
"We tried to tie him down to us, but unfortunately he turned down our offer and made a different choice. We have to accept that."
Thy said on the St Pauli website that he had always felt happy at the club, but that he wanted to "take the opportunity Werder are offering" to return to them.
Bremen are currently in the bottom three of the Bundesliga while Pauli are fourth in the 2. Bundesliga after 19 games of the season, three points behind the promotion play-off berth.