There is a multifaceted relational revolution afoot in International Relations (IR) and in the social sciences more widely. This article suggests, via engagement with varied forms of relational thought and practice in IR, but in particular via engagement with ‘relational cosmology’ associated with the ‘natural’ as well as the ‘social’ sciences, that there are important reasons for relational thought and practice in IR and around it to be more attentive to dialogues on relationality across natural and social sciences. If relational thought in IR has challenged the colonial and bifurcated ontologies of the field, relational cosmology too assists in shifting ‘modern’ understandings of science and the cosmos by facilitating engagement with situated knowledges and deep-going relationalities across ‘nature’ and ‘society’, ‘human’ and ‘non-human’ communities. Relational cosmology may be productive in joining, and perhaps even in facilitating, conversations across multiple relationalities emerging from different parts of the world and in different fields of inquiry, and yet – reflecting its relational and pluriversal orientations – it is not proposed here as a new ‘meta-‘ or ‘grand-’ narrative for relational theorising or IR.