The aim of this study is to investigate the role of linguistic and intelligence factors in the Iranian IELTS candidates’ speaking performance. Linguistic factors include depth and breadth of vocabulary knowledge, and grammar knowledge. Narrative and verbal intelligences represent the non-linguistic factors. The participants include 329 learners who took 5 validated tests and also participated in a simulated IELTS interview session. Model 1 (excluding the intelligence factors) represents the conventional view while Model 2 (including all factors) is proposed for the first time in this study. The SEM results show that, in contrast to the conventional view, intelligence factors do play a significant and undeniable role in developing the speaking construct. Finally, the applications and implications of the findings for promoting the construct validity of IELTS were discussed.

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