The purpose of this study was to see the role of English language proficiency level and sex on Iranian students’ beliefs about language learning. This study also investigated the usefulness of the BALLI questionnaire (Horwits, 1988), which checks learners’ beliefs, for the context of Iranian English language learners through conducting an interview. A total of 171 Iranian learners from safir institute took a TOEFL test (2003) and filled out BALLI questionnaire. Based on their TOEFL scores, they were divided into two levels of high and low language proficiency and each group was divided into two groups of males and females. Thirty-two participants including all groups were randomly selected for the interview. The results of the data analysis indicated that there was a significant difference in the learners’ beliefs about language learning at different language proficiency levels, but there was no significant difference in this regard between males and females. Also, the study did not prove any interaction between the two factors of sex and language proficiency level. The difference in the results of the interview and the questionnaire in three questions reveal that the questionnaire, though useful, is better to be used along with other measuring instruments.
