Filip Kostic has joined Hamburg from Stuttgart on a five-year deal for an undisclosed fee.
The 23-year-old completed a medical on Sunday and has signed a contract until June 2021, after a reported transfer fee of 17 million euros ($18.7 million) was agreed upon.
"We're glad we were able to complete the transfer," HSV director Dietmar Beiersdorfer told the club's official website. "He's a player whose actions are at a high tempo, who always looks for one-on-one situations.
"Despite being only 23, he has a lot of experience, he knows the Bundesliga and has proven his qualities in the past two years."
Kostic registered five goals and seven assists for Stuttgart in the Bundesliga last season, though he was unable to help the club avoid relegation to the second tier.