Despite the maritime industry’s significant role in the global economy, maritime accidents are a threat to life at sea and maritime economic performance. Furthermore, the human factor still accounted for as the main factor causing maritime accidents. Every year, many maritime accidents occur in Japan and Hong Kong, with collisions being the most common. In this study, Human Error Assessment and Reduction Technique (HEART) method is applied to the collisions data to identify the common mistakes committed by seafarers by determining the generic task, error-producing conditions and the value of Human Error Probability (HEP). This study aims to find the causes of collision in Japan and Hong Kong, compare them between the two countries, and apply HEART methodology to various maritime accidents. The data was sourced from the maritime accident data report of the Japan Transportation and Safety Board and the Government of the Hong Kong Special Administrative Region of the Marine Department from 2008 to 2016. There are 27 collision cases for Japan and 21 for Hong Kong. In general, human error is the most common factor leading to collisions. In conclusion, in Japan’s collision assessment, fairly simple tasks performed rapidly or with scant attention are identified as the most common generic task. However, in Hong Kong, most of the accidents occur during complex tasks. Japan has 101 EPCs for 27 cases while there are 115 EPCs for 21 cases that occurred in Hong Kong. Both Japan and Hong Kong have the time shortage, inadequate checking of progress, and poor information exchange among seafarers on the bridge as the common error-producing conditions occurred.