The home side took the lead against their local rivals when Roberto Firmino converted from a Sejad Salihovic free-kick.
Firmino claimed a second after 29 minutes but Kaiserslautern claimed what could be an important away goal when Mohamadou Idrissou rounded the keeper to score.
Hoffenheim, though, ensured a two-goal cushion heading into the second leg thanks to Sven Schipplock.
- Sports & Recreation
- Roberto Firmino
- Mohamadou Idrissou