The IMO Standard Marine Communication Phrases (SMCP) has been established purposely to enhance the greater safety of vessel’s navigation by standardizing the language used among seafarers. However, accidents are still occurred due to communication failures among onboard merchant vessels’ crews. It is worth mentioning that the major cause of marine accidents is human error (80%) where one-third from it was due to communication failures. Ineffective communication, different culture and language among seafarers onboard are some instigators of human error that lead to accidents in marine operations. Therefore, the primary aim of this paper is to investigate and evaluate the causal factors that contributes to communication failures onboard merchant vessels. Then, this paper recommends possible solutions for minimizing the communication failures among seafarers. To achieve this research objectives, two decision-making tools which are the Analytical Hierarchy Process (AHP) and Evidential Reasoning (ER) was applied. Data and judgments are obtained from domains experts from four marine training providers and eight shipowners in Malaysia. The result has shown that lack of SMCP knowledge, prejudice and dialect varieties are the most significant factors that contribute to the communication failures onboard merchant vessels. Few suggestions and opinions from the experts are proposed in this paper. This research can assist marine training providers and shipowners to identify and evaluate the causal factors of communication failures thus corrective action can be taken.