Talent management has become one of the key strategic challenges facing organisations, managers and employees in recent years. The effort a company makes to develop its critical talent (CT) is clearly not a good investment if they then leave for some other organisation. Understanding the causes of turnover and retention, specifically amongst CT, is therefore crucial, particularly in knowledge-based firms, whose top employees form part of their strategic assets. The current study integrates different research strands that have been previously reviewed separately. Specifically it looks at the retention of critical talent post acquisition in a multinational company (MNC). The research objective was to discover the key factors that influence CT retention, in a MNC post acquisition and explore how that influence plays out. The study explores the key factors that influence the retention of CT post acquisition, explores how the factors identified influence CT retention and it investigates the role of multiple stakeholders in CT retention post acquisition. A key contribution of this study is that in contrast to much of the literature which focuses exclusively on top executives, when describing CT, it conceptualises CT differently. The focus is on CT below vice president (VP) level, in a multi-national organisation. The particular focus is pivotal positions, defined as strategically important roles which differentially contribute to the organisation’s sustainable competitive advantage. The post-acquisition context is an interesting and novel period to conduct the research in. Additionally the opinions of those deemed CT that have left the organisation produced a unique perspective which is excluded from much of the extant literature. In developing a theoretical foundation for this work, it draws primarily from human capital theory, the resource based view of the firm and HR architecture. These lenses are applied to the MNE drawing upon separate but related strands of literature namely: talent management, retention and turnover, and mergers and acquisitions. The context of this study takes the form of a MNC operating in the global biopharmaceutical industry, based in Ireland and the United States. The primary methodological approach was a qualitative case study, using semi-structured interviews, with leadership, HR, current and former CT interviewed. This gave a well-rounded perspective and produced rich data to analyse. A survey was conducted which generated quantitative data around pivotal positions, CT and retention feedback, and this was incorporated in the findings. The headline findings were that criticality was understood differently and separating the role from person was difficult for managers and leaders. It demonstrated the complexity in defining this area within a single organisation. It also points to a lack of shared understanding at the organisational level as to what constitutes CT. CT was determined to be multi-level and not restricted to senior leadership roles. The ability to share tacit knowledge was seen as a vital responsibility for CT and without it they could be seen more as a single point of failure rather than CT. The issue of transparency, the business life cycle, acquisition setting and environment had a direct impact on CT retention. Whereas normally a negative sentiment could lead to turnover, one positive factor that could encourage CT turnover was seen to be a positive external environment, in terms of alternative career options. The role of the various stakeholders, in particular the role of the manager and use of good one to one communication was highlighted. Finally the need for a retention strategy and defined process was highlighted and this research led to the mapping out of a process specific for the organisation. Based on the research findings, the main theoretical contribution of this thesis is the adaption and development of a model to determine how retention could be strategically addressed, linked to the value and uniqueness of the critical talent involved, and considering the context in which it happens, specifically an acquisition and changing environment, drawing on the theoretical and empirical considerations of the study