Human error is recognized as the most common factor that causes maritime accidents. The human error assessment and reduction technique (HEART) is a human reliability assessment (HRA) that has been widely applied in various industries. Furthermore, the HEART – 4M method has been proposed to assess maritime accidents. The HEART – 4M method can clearly define the relationship between man, machine, media, and management factors and the human error. However, the calculation process to determine the weight of every selected error-producing condition (EPC) suffers from the uncertainty of the assessor's estimation in practical applications, which may affect the objectivity of its result. In this study, a modification of the HEART – 4M method with the technique for order preference by similarity to ideal solution (TOPSIS) is proposed. TOPSIS is a multi-criteria decision making (MCDM) tool. This study aims to develop the HEART – 4M method to make it more comprehensive and objective when assessing maritime accidents. First, the parameter of the generic task is determined as in the conventional HEART method. Second, the causal factors are converted to the suitable EPC – 4M, and there are four classification factors for the 38 standard EPCs, which are divided into man, machine, media, and management factors. Third, the TOPSIS is applied to handle the problems of interdependencies and interaction among EPC – 4M and the uncertainty that exists in the assessor´s judgment. The proportion effect of each EPC – 4M is determined through TOPSIS by considering the correlation among EPC – 4M. Finally, thirteen collision data obtained from the National Transportation and Safety Committee of Indonesia are assessed to apply the proposed method.