ABSTRACT: Important marine mammal areas (IMMAs)—‘discrete habitat areas, important for one or more marine mammal species, that have the potential to be delineated and managed for conservation’ (IUCN Marine Mammal Protected Areas Task Force 2018, p. 3)—were introduced in 2014 by the IUCN Marine Mammal Protected Areas Task Force to support marine mammal and wider ocean conservation. IMMAs provide decision-makers with a user-friendly, actionable tool to inform them of the whereabouts of habitat important for marine mammal survival. However, in view of their non-prescriptive, evidence-based and biocentric nature, the conservation effectiveness of IMMAs is strictly dependent on politicians’ willingness to make use of them. It has been the customary task of advocacy non-governmental organisations to lobby decision-makers to stimulate respect for environmental law, but the scientific community is increasingly joining this effort. Scientists can effectively strengthen a healthy relationship between scientific objectivity and political advocacy without damaging the credibility of conservation science. Thus, those undertaking the identification of IMMAs can be among those responsible for strongly advocating the implementation of IMMAs and other conservation initiatives.