Synchronous online language teaching involves the simultaneous employment of a range of techno-semio-pedagogical competences (Guichon, 2012). Indeed, given their flexibility and versatility, digital tools and the Internet can render teacher-student interactions dynamic. Among the necessary professional skills and strategies for online synchronous teaching, this paper focuses on the specific dimensions of affective competences and the social need to maintain a climate of comfort during one-to-one online tutoring interactions. We focus on a particular social phenomenon that is strongly linked to emotions - facework (Goffman, 1967). Applied to CALL, we analyse how this social practice unfolds in an interactional environment where the perception of the other is mediated by a videoconferencing platform. We noted four different types of facework triggering situations: lexical breakdowns, private anecdote tellings, overlaps and interruption of learner reflection time. Our multimodal analysis of facework reveals the frequent use of smile as a mimicry semiotic resource and highlights the phenomenon of interactional synchrony.