Purpose This paper aims to contribute to the multinational company (MNC) literature by studying the diffusion of a management idea within an MNC and its interaction with the MNC’s corporate immune system (CIS). Design/methodology/approach The qualitative single case study draws on evidence of how a management idea augments within an MNC and changes its development practice. Findings The study identifies four phases of the diffusion process and presents the interaction between the management idea and the CIS in each phase. Practical implications The more subsidiaries within an MNC that take the initiative to adopt a management idea, the harder will it become for the headquarters (HQ) to reject it. Thus, to ensure that changes in management practices are based on informed and, ideally, deliberate decisions, managers should critically evaluate management ideas immediately at inception. Originality/value The study breaks new ground by explaining how the CIS reacts to the diffusion of management ideas in MNCs.