The present paper concentrates on a web-based inquiry in the synchronous computer-mediated communication (SCMC) via Web 2.0 technologies of Talk and Write and Skype. It investigates EFL learners' socio-cognitive progress through dynamic assessment (DA), which follows Vygotsky's inclination for supportive interchange in the zone of proximal development. Sixty adult EFL learners at upper-intermediate level were randomly assigned to the control and experimental groups. The participants in the experimental group were involved in dynamic assessment in synchronous computer-mediated communication for seven weeks. The results reveal that, through interactions in the ZPD, DA in synchronous computer-mediated communication lets us explore not only the actual level of learners' listening ability but also to diagnose and assess the potential level of their listening development.