Given the importance of assessment in language education, this study was aimed at investigating the effects of interventionist and interactionist Dynamic Assessment (DA) on Iranian EFL learners’ perfectionism, willingness to communicate (WTC) and foreign language anxiety (FLA). The participants of the study were 166 pre-intermediate female and male learners at two public schools and one private language institute in Karaj. The participants were divided into three experimental groups and were given three separate questionnaires to measure their perfectionism, WTC, and FLA before the treatment sessions. During 14 sessions, groups A and B received instruction using interactionist DA and interventionist DA, respectively. Group C was instructed conventionally as the control group. At the end of the treatment sessions, they were given the same three questionnaires as the post test. The collected data were analysed using one-way ANCOVA. The results showed no significant differences among the two approaches of dynamic assessment and the control group in terms of their effect on learners’ perfectionism and willingness to communicate. Although there was no significant difference between the interventionist and interactionist models of DA, they were both significantly more effective than the control group on learners’ FLA. The findings suggested that dynamic assessment could reduce learners’ anxiety in language learning and lead to an effective teaching and learning process. These findings can have implications for teachers, students, and material developers.