The dual legitimacy of an international non‐governmental organisation (INGO) affiliate is critical to the INGO’s sustainable development, but few studies are found in the extant literature. Based on Kostova and Zaheer’s theoretical concept elaborating on organisational legitimacy under conditions of complexity, we conducted this study through the extended case method and used the grounded theory approach to examine the case study of the child organisation (CO) in Taiwan and its affiliate in Kyrgyzstan (CKO). Utilising an integrated framework elaborating on the INGO affiliate’s dual legitimacy (IADL), we examined the impact generated from the institutional environments in a multidimensional construct at the macro‐, meso‐, and microlevels. This study also explored the complexity of and interactions with the institutional environment that INGO affiliates might encounter. The findings of this study could serve as a guideline for INGO workers, policy makers and academicians.
Key Practitioner Message: • The first article applying the institutional theory and theory of organisational legitimacy on checking dual legitimacy of INGO affiliates through the case study of CO and CKO; • We examined the impact generating from the institutional environments with a multidimensional construct at the macro‐, meso‐, and microlevels through an integrated framework of INGO legitimacy from the perspective of the dual legitimacy that INGO affiliates face; • The findings of this study could be the resources of guideline for INGO workers, policy makers and academicians.