PurposeThe National Health Service (NHS) is facing unprecedented financial strain. These significant economic pressures have coincided with concerns regarding the quality and safety of the NHS provider sector. To make the necessary improvements to performance, policy interest has turned to encouraging greater collaboration and partnership working across providers.Design/methodology/approachUsing a purposive search of academic and grey literature, this narrative review aimed (1) to establish a working typology of partnering arrangements for improvement across NHS providers and (2) inform the development of a plausible initial rough theory (IRF) of partnering to inform an ongoing realist synthesis.FindingsDifferent types of partnership were characterised by degree of integration and/or organisational change. A review of existing theories of partnering also identified a suitable framework which incorporated key elements to partnerships, such as governance, workforce, leadership and culture. This informed the creation of an IRF of partnerships, which proposes that partnership “interventions” are proposed to primarily cause changes in governance, leadership, IT systems and care model design, which will then go on to affect culture, user engagement and workforce.Research limitations/implicationsFurther realist evaluation, informed by this review, will aim to uncover configurations of mechanisms, contexts and outcomes in various partnering arrangements and limitations. As this is the starting point for building a programme theory, it draws on limited evidence.Originality/valueThis paper presents a novel theory of partnering and collaborating in healthcare with practical implications for policy makers and practitioners.