Background: Open visiting refers to the principle of unrestricted visiting hours in the hospital setting to enable relatives, families and carers to visit at any time. There has been recognition that open visiting supports the principle of patient and family supported care and improves communication. Despite this there has been difficulty in implementing open visiting and barriers identified. The aims of this study were therefore to evaluate the implementation of open visiting, the barriers to implementation, sustainability and the impact of open visiting on communication between health care professionals, families and carers. Methods: The study was conducted on two large acute wards for the older person. Realist evaluation methods were used to understand 'what works well, how, for whom and to what extent.' Mixed methods were employed including qualitative interviews and descriptive analyses of routine data sets. Following the methodology of realist evaluation, programme theories were identified a long with the context, mechanisms and outcomes of implementation, to better understand the implementation process. Results: The results of this study identified some key findings, demonstrating that open visiting does improve communication and can help to build trusting relationships between families/carers and health care professionals (HCP). Barriers to implementation were based on the belief that it would impinge on routines within the ward setting. To achieve the principles of patient and family/carer centred care, the key mechanisms are the confidence and skills of individual nurses and health care assistants to engage with relatives/carers, whilst retaining a sense of control, particularly when care is being delivered to other patients. Conclusion: In summary, open visiting creates a positive culture which fosters better relationships between families/carers and HCPs. Involving families/carers as partners in care does not happen automatically in an environment where open visiting is the policy, but requires engagement with staff to encourage and support relatives/carers.