This study aims to present how intercultural and intracultural communication unfolds in EFL classrooms with NNESTs and NESTs who constantly negotiate common ground and positionings with their students. Three NEST and three NNEST teaching partners were observed and audio recorded during the first and fifth weeks of a new course they taught in turns. Data were transcribed and analyzed through conversation analysis using Kecskes and Zhang's socio-cognitive approach to common ground (Kecskes, Istvan & Fenghui Zhang. 2009. Activating, seeking, and creating common ground. A socio-cognitive approach. Pragmatics and Cognition 17(2). 331-355) and Davies and Harre's positioning theory (Davies, Bronwyn and Rom Harre. 1990. Positioning: The discursive production of selves. Journal for the Theory of Social Behaviour 20(1). 43-63). The findings revealed several differences in the ways NESTs and NNESTs established common ground and positioned themselves in their social interactions. NESTs' lack of shared background with their students positioned them as outsiders in a foreign country and enabled them to establish more core common ground (i.e., building new common knowledge between themselves and their students). NNESTs maintained the already existing core common ground with their students (i.e., activating the common knowledge they shared with their students) while positioning themselves as insiders. NESTs' difference-driven, cultural mediator approach to common ground helped them create meaningful contexts for language socialization through which students not only learned the target language but also the culture. On the other hand, NNESTs adopted a commonality-driven, insider approach that was transmission-of-knowledge oriented, focusing on accomplishing a pedagogical goal rather than language socialization.