This study aimed to illuminate the diagnostic potential of the interactionist dynamic assessment (DA) to identify the candidates’ academic reading difficulties on the IELTS Reading test. Furthermore, DA and its interactive environment seem to provide an opportunity to diagnose the possible linguistic and cognitive roots of the academic second language (SL) reading difficulties that the modest user IELTS candidates faced. In so doing, three participants whose scores in the academic IELTS reading sub-score were 5/5on a scale of 1-9 participated in this study. The data were collected through observation and interaction based on DA principals through 36 individualized sessions (12 sessions for each participant). In each session, they were assigned to answer 13-14 academic reading comprehension questions independently, and then the mediator and the learners collaboratively reviewed the questions answered in the first stage. The feedback types offered deliberately ranged from very implicit to very explicit. The interactions were video recorded, transcribed word-by-word, and investigated. The findings indicated participants' difficulties in locating specific information, interpretation of words or phrases in the text, understanding the key ideas in a paragraph level, inference making, and interpretation of the writer's intention and viewpoint. From a diagnostic perspective, it is recommended that the interactionist DA could be used as an independent or complementary diagnostic tool to diagnose academic reading difficulties and their linguistic and cognitive roots.
