This article explores identity dynamics in public health working at the level of the institutional identity ascribed to public health professionals, and the identity work that public health workers perform. Drawing on focus group research with school nurses and community midwives in England, the article identifies two important but neglected areas for interrogating public health worker's identity work: boundary management and interplexity. We suggest that school nurses and community midwives do identity work from marginal positions: positions that exist in the shadow of bio-medicine, but from which new strands of identity are performed in spaces of micro-emancipation. However, while new strands of identity are revealed through individual performance, the very marginality of these professionals in terms of institutional, conceptual and physical resources are shown to prevent development of sustainable public health discourses. On this basis, we suggest that marginal professions might seek self-protection from dominance in nostalgia for modernity.