As shown in the Antigua and Barbuda-Tuvalu Agreement of 31 October 2021, the possible role of an advisory opinion of the International Tribunal on the Law of the Sea (ITLOS) as a full court in addressing climate change is attracting growing attention. Adverse impacts of climate change on the oceans can be considered as ‘marine pollution’ under the United Nations Convention on the Law of the Sea. However, to obtain an advisory opinion addressing climate change from ITLOS as a full court is not a straightforward matter because there is a need to cross some procedural hurdles. In light of this, it is necessary to examine some preliminary issues with regard to the Tribunal's advisory jurisdiction. This article therefore offers some preliminary considerations on an ITLOS advisory opinion in addressing climate change, focusing particularly on the legal basis for the advisory jurisdiction of ITLOS as a full court and the admissibility of an advisory opinion.