When they interact in everyday situations, people constantly create new fragments of social reality: they do so when they make promises or agreements, but also when they submit requests or answer questions, when they greet each other or express gratitude. This type of social reality ‘in the small,’ that we call interpersonal reality, is normative in nature as all other kinds of social reality; what makes it somewhat special is that its normativity applies to the very same persons who create it in their interactions. We first show that interpersonal reality can be accounted for in terms of a suitable concept of interpersonal responsibility, which in turn can be understood as a form of second-personal responsibility (in Darwall’s sense), intentionally co-constructed by two or more agents for themselves. Then we introduce certain significant subspecies of interpersonal responsibility, namely mutual and joint responsibility, and compare them with Gilbert’s notion of joint commitment. Finally we discuss how relationships of interpersonal responsibility can be brought about through communicative acts, understood as actions performed with underlying communicative intentions.