The Bosnia and Herzegovina international, 24, has penned a three-year deal with the Bundesliga club.
Bicakcic was part of the Braunschweig side that got relegated from Germany's top flight last season.
"Ermin's going to make our defence even more stable," Hoffenheim director of football Alexander Rosen is quoted as saying by Sky Sports News. "He emphasised the passion he has got in 31 appearances for Braunschweig during the season just ended."
Hoffenheim secured a ninth-place finish in the Bundesliga table last season.