This study tried to investigate the effect of reading story aloud on Iranian EFL learners' vocabulary learning. The research began with 40 learners, twenty in an experimental group and another twenty in a control group. After dividing the sample into groups, both groups took pretest of vocabulary. In the next phase of data collection, in the experimental group, the teacher read stories aloud to intermediate EFL learners but in the control group, the traditional method of reading a text was applied. In the last phase, the vocabulary posttest was administered to measure the extent of the new vocabulary the learners acquired from the reading. Independent samples t-test was used to analyze the data. Results showed that there was a statistically significant difference between the groups. Oral story reading constitutes a significant source of vocabulary acquisition. Book writers and teachers could benefit from the result of this study.