The C-Class scored five stars for adult protection, with full marks for side-impact safety.
However, it scored only three stars for child protection.
The testers noted that the car Mercedes submitted for testing did not have the company's optional automatic child-seat-recognition system fitted.
As a result, it was not possible to deactivate the airbag and place a child seat in the front.
The C-Class scored two points for pedestrian safety.