Dynamic Assessment (DA) method which combines instruction and assessment can reveal the extent to which the language learners have acquired what they have been taught. This quasi-experimental study examined the role of interactionist and interventionist DA on Iranian English as a Foreign Language (EFL) students’ descriptive writing ability. This study also explored whether there is any relationship between students’ attention to specific components of descriptive writing and their writing performance. To this end, 90 EFL learners who were at the intermediate level of language proficiency, based on the results of the Oxford Placement Test (OPT), constituted the sample of the study. The participants were requested to write a descriptive essay as a pretest. Then, they were randomly assigned to control, interventionist, and interactionist groups. During the mediation step, the control group was provided with the traditional teaching methodology, but the experimental groups were trained based on the DA method through distinct mediators. The students were finally asked to write a descriptive writing on a new topic for the post-test. To analyze the data, the descriptive statistics, paired samples t-test, one-way ANOVA, correlation, and regression analyses were run. The findings of this study indicated that the dynamic assessment proved to be effective in enhancing the writing competence of the participants; however, the impact of the interactionist approach was significantly higher than the interventionist one. The findings also revealed the significant relationships between students' attention to specific components and their overall writing performance, except Mechanics. These findings highlight the effectiveness of dynamic assessment approaches, particularly the interactionist method, in enhancing EFL students' descriptive writing skills. پرونده مقاله