This paper seeks to explore the perception of culture held by conference and diplomatic interpreters in post-WWII Japan. Based on oral history research with five Japanese pioneers, interpreters’ perceptions about culture and cultural barriers in communication are studied and then compared with their role perceptions and their actual practice. Although the pioneering conference interpreters perceived their role as more or less invisible, showing little interest in the discussion of culture and cultural mediation, their narratives in life-story interviews demonstrate that they were essential participants in intercultural communication, bridging cultural barriers. Without being aware of their role as cultural mediators, the five interpreters were actively and autonomously involved in intercultural communication as indispensable co-participants.