Human reliability analysis is essential to predict ship crew performance at the operation level for critical shipboard operations which pose a high risk. Specifically, the crew who are working on tanker ships has to be extra vigilant against the hazardous nature of the cargo. This paper performs a detailed human reliability analysis step by step for cargo discharging operations in crude oil tankers. To achieve this purpose, a Standardised Plant Analysis Risk Human Reliability Analysis (SPAR-H) extended by the Evidential Reasoning (ER) approach is used to systematically predict the probability of human errors. While SPAR-H provides a robust tool to calculate human error probability simultaneously, the ER fuses raters’ opinions in decision-making. The finding of the research shows that the overall human reliability is found at 6.52E-01 for cargo discharging operations in crude oil tankers. Besides its practical contributions to maritime crude oil transportation, the proposed approach presents how a comprehensive insight into human reliability can be gained.