PurposeThe literature on Mergers and Acquisitions (M&A), cultural differences between organizations have frequently been identified as one of the main challenges in the process of post-merger integration (PMI). Existing research has explored a broad variety of cultural differences in perceptions, such as those relating to expectations, norms, values and beliefs within the respective organizations, and how these affect the process and success of PMI. However, less attention has been paid to the relevance of the macro-societal context to PMI. The ambition of this article is, therefore, to advance our understanding of how macro-level societal factors define organizational cultures and affect the success of PMI.Design/methodology/approachWe draw on social systems theory as devised by Niklas Luhmann, assuming that organizations are always embedded in the macro-level societal context of distinctive realms of social reality—such as the economy, politics, religion and the arts—that make up the so-called “function systems”. Looking at the case of the integration of a Brazilian technology start-up into a market-leading corporation, we analyze the dominant orientations towards these function systems, and the changes in these orientations over time.FindingsThe results suggest that differences in organizational culture in PMI can be partly explained by differences in orientations to the function systems. Moreover, forcing dramatic changes of orientations towards the function systems within a merged entity can severely damage its raison d'etre in the first place, potentially leading to, in some sense, an account of “culture murder”.Originality/valueThis article is unique in demonstrating that organizations are multifunctional systems whose culture is defined by the highly specific and potentially varying degrees of importance they place on individual function systems and that knowledge or neglect of these functional profiles may seriously affect the success of post-merger integration. Against this backdrop, the article presents a multifunctional profiling method that may easily translate into PMI management tools.