Professional practice is embedded in complex dynamics of knowledge that are present within, but reach beyond, local work. Knowledge is generated from a manifold of sources, and further developed and circulated in professional communities as practitioners are confronted with non-routine problems. Drawing on the work of Karin Knorr Cetina and her associates, we suggest that a perspective of epistemic practices and object relations is useful for conceptualising the epistemic dimensions of professional work and learning. We consider how the perspective has inspired research on professional practice and use examples from the nursing profession to illustrate how it may be employed to examine: (i) how practitioners develop knowledge and practice by engaging with epistemic objects; (ii) how relations with objects give rise to community formation and (iii) how object relations link practitioners with a wider knowledge world. We argue that the perspective is productive for investigating knowledge practices as constituted by dynamic object relations across sites and levels in the expert culture. To further improve its potential in professional contexts, however, we suggest the need for the development of analytic concepts that differentiate between modes of epistemic engagement and account for the presence of multiple knowledge objects in professional practice. (Contains 2 notes.)