This research investigated the relationship between vocabulary learning strategies and vocabulary size of Iranian university EFL students. Participants in the present study were a total of 67 EFL learners, studying at Shiraz Azad University as senior English Translation students. The instruments utilized for data collection were three tests: A TOEFL test of proficiency, a Vocabulary Level Test, and a learning strategy questionnaire. The vocabulary learning strategies employed by the two groups of low and high vocabulary level sizes were compared, using a T-Test analysis. Analysis of the results revealed that, those participants who employed a variety of strategies, rather than a limited number of strategies, had a high vocabulary level size. The findings of the study also revealed the most and the least used strategies by the high group of vocabulary level size and the effective strategies employed by the so-called group were identified. (Contains 3 tables.)