Today, great a number of assessment methods have been practiced in educational systems. However, Dynamic Assessment (DA), as the modern assessment method with its emphasis on improvement and development of learning through joining teaching and assessment, is of paramount significance. Thus, one can call DA as a major and revolutionizing factor in teaching and assessment. So far, some conducted studies have dealt with the efficacy of DA on different language areas. In line with the relevant studies conducted, the present study worked on the effect of interventionist DA on introvert versus extrovert learners’ academic essay writing in English language translation students at Islamic Azad University Shahr-e-Qods Branch. As a result, it was confirmed that DA had a statistically significant effect on the academic essay writing of both Iranian introvert and extrovert EFL learners. Furthermore, there was a statistically significant difference between the performances of the extroverts vs. introverts on academic essay writing while applying interventionist DA. In other words, the extroverts had higher scores in their posttests compared to the introverts. Moreover, the results of the attitude questionnaire revealed that the extroverts had more positive attitude towards the application of DA than the introverts.