Travel by Car: The driving distance between Karlsruhe and Mostar is 1.300 km with estimated travel time of 12 hours and 30 minutes. Fastest route goes via highway in Croatia, Slovenia and Austria where tool fees apply. The route also goes via highway in Germany, but it is free of charge.
Travel by Bus: Timetable and price tickets for direct buses from Karlsruhe to Mostar, if any, you can check here. Alternatively it is possible to travel via Split or Zagreb in Croatia.
Alternative ways of travelling from Karlsruhe to Mostar:
Travel by train: From Mostar there is a possibility to travel by train to Zagreb (via Sarajevo), and then continue with international train to Karlsruhe (via Munchen). Travelling by train in Bosnia and Herzegovina and Croatia is relatively slow, so travelling time in total is much longer compared to travel by bus or car.
Travel by plane: There is no direct flight, but there is option to fly to Sarajevo or Split in Croatia.
Map with buses from Mostar: