Conversational implicatures (CIMs) are implied by the speaker in context rather than being linguistically encoded, and learners’ inability to infer the intended meaning, if not remedied through instruction (or mediation), leads to communication breakdowns. Given this premise, the current study aimed to examine effects of classroom praxis-based instruction adjusted to EFL learners’ Zone of Proximal Development (ZPD) on their comprehension of CIMs. Participants were 36 Iranian high school students in 2 classrooms, assigned to experimental and comparison groups. A 20-item CIM (...) test was administered at pretest and posttest times to collect the data. Microgenetic trajectories were also traced through audio-recorded role-plays and social interactions within the ZPD setting. ZPD-adjusted mediational instruction on CIMs was given based on a multi-level regulatory scale and a view of microgenetic development along an other-to self-regulated functioning continuum. In the non-ZPD setting, mainstream teacher-fronted instruction was employed. ANCOVA results revealed differential instructional effects in favor of the praxis-based mediational setting. Microgenetic learning episodes also portrayed how collectively-mediated, ZPD-activated learning led to L2 learners’ progressively improved comprehension of CIMs. The findings suggest that comprehension (and perhaps production) of L2 CIMs can be improved through praxis-oriented co-construction of pragmatic knowledge through collaborative engagement with communicative activity. (shrink)