IntroductionPeople are increasingly mobile for numerous reasons, including healthcare. Patient mobility has vast implications for individuals, communities and whole populations and yet, to date, research on patient mobility has been quite limited. Only a small body of evidence exists on patient mobility between low-income and middle-income countries, instead having focused primarily on cross-border movement between high-income and low-income countries. In this paper, we present a protocol for examining this under-studied phenomenon.Methods and analysisWe propose to examine patient mobility between low-income and middle-income countries using a realist synthesis approach. Specifically, we aim to document why patients from low-income and middle-income countries cross international borders for healthcare, by identifying the mechanisms through which patients decide to cross-borders, and the contextual characteristics of domestic health markets that influence this choice. An underlying theory was established, based on the lead author's experience and a brief literature review, which will provide the basis to analyse search results in a subsequent paper. Search results will be obtained from databases (Ovid Medline, EMBASE, Scopus, EconLit, Web of Science) and the grey literature. An expert committee will be enlisted, prior to screening results, to review search results to ensure comprehensiveness. Based on this preliminary theory, we propose that, in some low-income and middle-income country markets, the interaction between demand-side and supply-side determinants results in market imperfections that, in turn, lead to patient movement across borders.Ethics and disseminationThe study does not involve primary research and, therefore, does not require formal ethical approval; we do, however, follow the relevant standards of utility, usefulness, feasibility, propriety, accuracy and accountability. The standards of realist and meta-narrative evidence synthesis (RAMESES) will be adhered to in reporting the findings of the review. Once completed, the findings of the resulting manuscript will be published in a peer-reviewed journal.Trial registration numberThis protocol has been registered with PROSPERO, registration number CRD42014014391.