A growing number of studies on students' intercultural interactions and learning in higher education contexts have placed cosmopolitanism and agency at the centre of conceptual and empirical inquiry. The concept of 'cosmopolitan agency' has been proposed as a hallmark of intercultural relationships, such as friendships, between international and domestic university students, which are found difficult to develop in many countries. However, the literature has not established the conditions necessary for the (non-)emergence of this student agency. This paper fills this knowledge gap by presenting an ecological and person-in-context conceptual framework of cosmopolitan agency in intercultural student interactions on campus and beyond. Drawing on multidisciplinary literature (e.g. higher education, psychology, sociology, cosmopolitanism, urban and disability studies), the paper submits a theoretical proposal that cosmopolitan agency (as present practice) emerges at the dynamic experiential interface between cosmopolitan capital (as an individual resource built on past experience) and affordances in convivial proximity (as the environment triggering future projection). This proposal is elaborated through the empirical illustration of four (i.e. amicable, critical, latent and inactive) states of cosmopolitan agency that manifest different forms of intercultural interactions. The paper is expected to advance theoretical inquiry into the issues of power, privilege, morality and reflexivity in students' engagement in intercultural interactions, and to support a third option for interactions between passive presence and fully-fledged relationships. The directions for future conceptual and empirical research that are ultimately expected to serve for the improvement of student experience are also provided.