Moral development during emerging adulthood is a topic of growing interest. Several different theories within the study of human development appear to converge on this point of inquiry, as the study of moral development during emerging adulthood recruits different areas of expertise. This paper explores different theoretical approaches to the study of moral development during emerging adulthood and demonstrates the need for interdisciplinary collaboration. The overall shape of the exploration is governed by broad philosophical considerations grounded in the ethics of Aristotle. First, Aristotle’s ideas are adapted to a developmental paradigm, providing an overarching theory of moral development. Second, the study of moral development during emerging adulthood is situated within the relational developmental system metatheory of human development. These first two theories provide a framework for “moral” and “development,” respectively. Additional conceptual and theoretical issues are addressed as they arise, including moral identity and the link between virtue and happiness.