Drawing on sociocultural theory, this study explored the impact of interactionist and interventionist approaches to group dynamic assessment (GDA) on Iranian intermediate English as a foreign language (EFL) learners' listening comprehension development. To this end, 90 intermediate EFL learners were divided into two experimental and a control group. To ensure homogeneity of the proficiency level of participants, an abridged version of a sample TOEFL Junior Standard Test was administered to the participants. The listening comprehension section of the TOEFL Junior Standard Test served as the pre and post -tests. Participants of each major group were then assigned into five subgroups of four and two subgroups of five members. During 13 treatment sessions, in the first experimental group the researcher participated in the subgroups' class activities and applied interactionist approaches to interact and assist the group members in their listening comprehension activities. In the second experimental group, based on the sandwich model of interventionist approach to dynamic assessment, the researcher, while participating in the groups' activities, provided the group members with a range of more implicit to explicit appropriate feedback. However, in the control group, the traditional summative forms of assessment were applied and interactive or interventionist DA assessment were avoided. The analyses including one sample T-Tests, ANOVA, and Tukey HSD post-hoc revealed that interactionist GDA was the most effective procedure for the intermediate EFL learners' listening comprehension development. Moreover, although interventionist GDA procedure seemed to be more effective than NDA procedure of the control group, the superiority was not statistically significant. The findings underscore the primacy of interactive patterns of GDA and imply that the more the practitioners side away from unilateral and authoritative approaches of pedagogy in favor of the interactive and cooperative approaches, their educational endeavors will be more effective and consistent with the pedagogical objectives set for the listening comprehension development of EFL learner.