This article explicates marginalization as a guiding concept for the development of nursing knowledge that values diversity. The seven key properties of marginalization as it applies to the domain of nursing are (1) intermediacy, (2) differentiation, (3) power, (4) secrecy, (5) reflectiveness, (6) voice, and (7) liminality. Through examination of each of these properties, the relationship between marginalization and vulnerability is clarified, and by this means the relevance of marginalization for health is established. The implications for shaping future nursing research, theory, and practice related to the health of diverse populations are discussed.