PurposeThis paper seeks to explore the use of common corporate language(s) in multinational corporations (MNCs). These organizations are usually multilingual and characterized by high language diversity. Parallel streams of literature in international management and international business communications are built upon to problematize the notion of a common corporate language.Design/methodology/approachInformation gathered from 36 personal interviews of the German‐based multinational Siemens is the primary source of data for this case study. The interviews were conducted in three different languages in three different organizational units of Siemens AG in Finland and Germany.FindingsIt was possible to identify powerful interplay between two languages – German and English – and to uncover discrepancies between company policy and employee practices with regard to language use. On the basis of these findings, the challenges of managing language in multinationals are discussed.Originality/valueArgues that a common corporate language may not be as widely shared within the firm as the term suggests, given the multilingual nature of most multinationals, variation in the language proficiency of their employees, and the level of analysis used in previous research.