The present study examines whether task supported language teaching (TSLT) has an impact on L2 English learners’ use and knowledge of request mitigators, assessing the impact of student-students vs. teacher-students interactions on students’ attention to pragmatics during task-based interaction. Forty-eight students of English at a Spanish university participated in the study. Participants were randomly assigned to one of three groups: the student-students interaction group (N = 16), the teacher-students interaction group (N = 16), and the control group (N = 16). Data were collected in pre-test, post-test and delayed post-test email tasks and analysed for frequency of use of request mitigators. Participants’ self-evaluations of email appropriateness were also used to examine whether TSLT facilitated knowledge of request mitigators during student-students and teacher-students tasks performance. In addition, interactions during the TSLT treatment were recorded and analysed for pragmatic related episodes (Taguchi & Kim, 2014) on request-making expressions. Findings from the study showed positive effects of TSLT on learners’ use of request mitigators. In addition, differences were found in the impact of the participatory structure on students’ level of interactional engagement during task performance, which seems to have an impact on pragmatic learning outcomes. More specifically, in teacher-students interaction students hardly ever paid attention towards pragmatics, but if they did, it had an impact on the students’ knowledge of request mitigators. On the contrary, metapragmatic discussion in student-students interaction seemed to trigger attention towards pragmatics and enhanced students’ awareness of how to mitigate email requests.