Background: While numerous studies have explored the patient experience of dialysis or other end-stage kidney disease (ESKD) treatments, few have explored the process of transitioning between dialysis modalities. This study aimed to develop an in-depth understanding of patient and caregiver perceptions and experiences of the transition from peritoneal to haemodialysis (HD) and to identify ways in which transitions can be optimised. Methods: Fifty-four in-depth, semi-structured interviews were undertaken at six study sites across the West Midlands, UK ( n = 23), and Queensland, Australia ( n = 31). Thirty-nine participants were patients with ESKD; the remainder were family members. An inductive analytical approach was employed, with findings synthesised across sites to identify themes that transcended country differences. Results: Of the 39 patient transitions, only 4 patients reported a wholly negative transition experience. Three cross-cutting themes identified common transition experiences and areas perceived to make a difference to the treatment transition: resistance to change and fear of HD; transition experience shared with family; and bodily adjustment and sense of self. Conclusion: Although each transition is unique to the individual and their circumstances, kidney care services could optimise the process by recognising these patient-led themes and developing strategies that engage with them. Kidney care services should consider ways to keep patients aware of potential future treatment options and present them objectively. There is potential value in integrating expert support before and during treatment transitions to identify and address patient and family concerns.