The aim of the present study was to find out whether language learners' self-efficacy beliefs affect the reading comprehension achievement of EFL learners in Iran. A convenience sample of 120 learners from different language schools participated in this study. A self-efficacy questionnaire was adopted to analyze students' self-efficacy beliefs. To measure their reading comprehension, the reading part of Michigan Test, as a test of English language proficiency was adopted and given to the participants. The Pearson product-moment formula demonstrated that there was a significant relation between self-efficacy and reading comprehension, and the correlation between self-efficacy and reading comprehension was positive. Therefore, it might be postulated that the higher self-efficacious the learners are, the better they answer the reading comprehension questions. The results of the statistical analysis also led the researcher to conclude that the relation between language learners' self-efficacy beliefs is not affected by gender.