This study aimed at investigating children and young adult EFL learners of Iran Language Institute(ILI) and their course books in the light of Multiple Intelligence (MI) Theory. To achieve this aim, 240 EFL learners participated in this study. First, the students' intelligence profiles were identified by adapting and using Lazear's (1994) children's questionnaire and Christion's (1996, 1998) young adults' MI survey. Secondly, all the nine children's course books along with seven young adults' taught in Iran Language Institute (ILI) were evaluated through the MI checklist to determine the extent to which MI theory is reflected in these course books. The analysis of the course books' activities revealed that both series of course books mostly catered to verbal/linguistic and visual/spatial intelligences. The least dominant intelligences were intrapersonal and naturalist intelligence types, and no example of the naturalist intelligence was found in the young adult coursebooks' activities. The results of the study also showed the discrepancies between students' and course books' MI profiles. As opposed to the course books' MI profile, a balanced distribution of intelligence types were observed among both children and young adult students; i.e., students preferred all types of intelligences in varying approximate degrees. The findings of the study have some pedagogical implications for teachers, coursebook designers, teacher educators and material developers to consider MI theory and language learners' MI profile in designing course books and using classroom activities.