Relational aspects of professional practice demand increasing attention in research on work and learning. However, little is known about how knowledge is enacted in practices where different people work together. Working in partnership with clients surfaces a number of epistemic demands, responses to which are poorly understood. This paper analyses two cases of nurses working with parents in support services for families with young children. The questions asked are: What epistemic practices are enacted when professionals work in partnership with clients? How do they generate distinct modes of partnership work? Findings show how professionals' and clients' knowledge is mobilised and made actionable through practices of diagnostic reasoning, recontextualising, testing and contesting knowledge claims. A distinction is presented between partnership that unfolds as strengthening the client from a professional epistemic perspective, and that which validates and augments the client's own epistemic contribution. This reveals how knowledge is made to matter and becomes a basis for action in the course of working with others, and informs a new analytical distillation highlighting key epistemic aspects of professional-client partnership. Keywords Partnership; professional knowledge; epistemic practices; professional practice; parenting communication and inter-personal relationships have been specified in models, such as the Family Partnership Model (FPM; Day et al. 2015). The FPM was developed at the Centre for Parent and Child Support in the UK, and combines a model of an iterative helping process with in-service training for professionals and volunteers. The FPM focuses on communication and negotiation, describing relationships between professionals and clients, and qualities that contribute to these such as empathy, active listening, and positive regard for parents. Prior analyses of practices where FPM was implemented revealed partnership to be enacted in different ways. Relationships between exploring the problem, developing new meanings, embodied caregiving, and future planning varied from case to case (Hopwood 2016). Partnership reflects the contingencies and dynamics specific to each family (Hopwood & Edwards 2017). However, research shows professionals can experience difficulty wielding their expertise under the rubric of partnership (Grundmann 2017). Neither models like FPM nor prior research have clarified how professionals and parents handle knowledge. The epistemic dimensions of partnership remain unclear. This paper documents the enactment of partnership in concrete work settings, and addresses this gap by asking: What epistemic practices are enacted when professionals work in partnership with clients? How do these practices position participants and generate distinct modes of partnership work? Specifying distinctions between two cases, we then highlight key epistemic aspects of professional-client partnership. An epistemic practices perspective An epistemic practices perspective is useful for conceptualising ...