Piracy and maritime terrorisms are the eldest form of maritime criminal activities occurred across the globe and becoming enormous threats to navigational security. Since the past decades, major actors in maritime policy such as ocean governance and international security have discussed to include countermeasures in combating maritime terrorisms. However, maritime security remained as a critical agenda that have no definite solution. Recently, these ongoing terrorisms have threatened the sovereignty of many countries including Malaysia. Concerning about the issue, this paper aims to analyses the piracy and maritime terrorisms in Sulu Sea by identifying and assessing the effects of piracy and maritime terrorisms on the Malaysian navigational security in Sulu Sea. Therefore, an Analytical Hierarchy Process (AHP) and Evidential Reasoning (ER) approaches are used in this analysis. An AHP is use for prioritizing the effects of maritime terrorisms. Then, the ER approach was proposed to assess each maritime terrorism effect in a fuzzy context. In this paper, Sulu Sea has been highlights as the case study. This article presents an exhaustive review on the piracy and maritime terrorisms in Sulu Sea. The results of the numerical assessment have indicated that the crew casualty and injury are the most alarming risks in that area due to the piracy and maritime terrorisms, followed by the vessel security, port security, navigational delay, vessel route diversion, financial loss and cargo loss and damages. It is suggested that the involvement of government and maritime stakeholders in Malaysia are necessary for ensuring safe and secure navigation. This paper is expected to assist and guide enforcement agencies and other related entities to enhance the navigational security by conducting the proactive assessment in combating and reducing maritime terrorisms especially in Malaysian waters.