Former Hamburg midfielder Bernd Hollerbach has returned to the club as head coach on a contract until 2019.
Hollerbach spent eight years at Volksparkstadion from 1996 to 2004, scoring seven goals in 224 appearances in all competitions.
He has since taken on a number of coaching roles in the German lower leagues and most recently oversaw Wurzburger Kickers' relegation from the second tier at the end of last season.
Hollerbach also spent time as assistant to former Hamburg boss Felix Magath at both Wolfsburg and Schalke.
The 48-year-old replaces Markus Gisdol, who was sacked on Sunday after rock-bottom Cologne inflicted a fourth successive league defeat on Hamburg to leave them second bottom.
Hollerbach will be joined by assistants Steffen Rau and Matthias Kreutzer.