All the electrical demand of ship are provided by diesel generators (DG). Failure of generators due to breakdown can lead to the blackout of the ship which may suddenly cause serious damage to ship's main and/or auxiliary engines, human health and marine environment or any structure at ship's route. Thus, the planned maintenance and repairs of the generators must be done properly without any deficiency or delay. And even then, since the generators run continuously failures may often occur. In this context, this paper provides a DEMATEL (Decision Making Trial and Evaluation Laboratory) method to evaluate the critical operational faults in marine DGs. The DEMATEL method enables to identify and analyze the important faults of marine DC within the respect to the cause-effect relationship diagram. The obtained results of the research will contribute to ship safety at sea and prevention of hazardous machinery effects.