We study how differences between organizational subcultures influence the effectiveness of the Enterprise Architecture (EA) function for steering the enterprise. In this paper, we contribute findings from a case study in a governmental organization. We derive seven propositions concerning the relation between cultural differences and EA effectiveness. For one, we suggest that cultural differences among the architects have a negative impact on the architects’ communication towards the management. In addition, our data suggest that the influence of cultural differences is indirect: communication defects and disagreement within the architecture board act as important intermediary factors