We examine how the authority of investors to speak about climate change with corporations is established. Leveraging the ‘communication as constitutive of organisations’ (CCO) perspective, we analyse who speaks on behalf of whom (or what) in shareholder engagement on corporate carbon emissions. Based on access to private dialogues between an engager acting on behalf of a pool of investors with 20 utility corporations, we identify how three authoritative personae—that of diplomat, advocate, and coach—convey climate change concerns. We find that the mirroring of these authoritative personae by corporations may lead to deliberation, evasion, or rejection of the suggested courses of action. We theorise how relational authority is communicatively constituted in shareholder engagement through a process of mirroring and switching between authoritative personae. Our framework contributes to the study of CCO and relational authority by highlighting how meta-figures are used by external actors in an attempt to author appropriate corporate actions. We discuss the implications of our framework for the role of shareholder engagement in current attempts at greening financial capitalism.