Bayern Munich head to Qatar for the Fifa Club World Cup with a 10-point lead at the top of the Bundesliga after victory in snowy Berlin.
Bayern were dominant if not at their fluent best throughout, with Robert Lewandowski missing an early penalty.
Kingsley Coman scored the only goal with a deflected shot from range that looped over Rune Jarstein and in.
The German champions could not find a second goal and had a scare when Matheus Cunha ran clear but shot wide.
Hertha are only out of the relegation zone on goal difference.
Bayern face African champions Al Ahly in Monday’s Club World Cup semi-final – a match you can watch live on the BBC Sport website and Red Button. Champions League winners Bayern could win their sixth trophy in nine months