Abstract Globally, there has been a substantial growth in interest in autonomous surface ships. This new domain presents numerous concerns for enhanced reader comprehension. The most crucial topic to consider is the safety of autonomous ships and the risks they present. To enable the use of autonomous ships, they must be as safe for the environment and for people as manned surface ships. However, as it has not yet been widely implemented, acquiring real-time data restricts the scope of the study. The objective of this paper is to conduct a comprehensive quantitative risk analysis for maritime autonomous surface ships (MASS). Therefore, it focuses on the operations to be performed by MASS and the factors that may pose a risk. In this context, Hazard and Operability Analysis (HAZOP) and Cognitive Reliability and Error Analysis Method (CREAM) approaches will be used in risk analysis assessment. While the HAZOP method will be used to determine the deviations, causes, possible consequences, and measurements that autonomous surface ships will be exposed to, the extended CREAM will be used to determine the likelihood of occurrence and risk levels of the MASS operation. The outcomes of the paper are anticipated to enhance the safety operational safety level of autonomous ships as well as mitigate risks.