More than five decades ago, Environment Impact Assessment (EIA) emerged in domestic legislation as a tool to respond to increased human pressures on the natural realm. Although the theory and practice of conducting EIAs have evolved over the years, several shortcomings for an effective implementation remain, hampering it from consolidating as a tool to promote Ecosystem-based Management (EBM). The challenges undermining an effective implementation of EIAs are magnified when considered under the scope of offshore extractive activities taking place in areas beyond national jurisdiction, such as deep seabed mining (DSM) on the international seabed (or ‘the Area’), which is governed by an international organization known as the International Seabed Authority (ISA). DSM activities are anticipated to cause extensive environmental harm, which may compromise the still poorly understood processes, functions, and services in the deep ocean. Since its inception, the ISA has taken measures to address the assessment of environmental impacts arising from DSM activities at the various stages of the mining process, which range from prospecting, exploration, and future exploitation. Nevertheless, a detailed description of the procedures to assess impacts at different stages of mining is absent in the literature, remaining a puzzled topic. This paper seeks to clarify the ISA's procedural framework for the assessment of environmental impacts arising from the different mining stages and reveals that its current practices do not represent a comprehensive, transparent, or participative EIA process that conforms with EBM. Consequently, the ISA's existing approach to the EIA process and its potential to support informed decision-making is doubtful. Based on the identified shortcomings, this paper provides some recommendations for improvement of EIA practices at the ISA.