abstract this study aimed at investigating the impact of etymology strategy instruction on the development of vocabulary of iranian intermediate efl learners. etymology, knowledge of origin of words, roots, and affixes, has proved to be a controversial issue and a question of long debate with regard to its impact on the process of vocabulary learning. this study employed etymology strategy in an experimental design for the students to study different tables of common roots, affixes with their meaning in order to get the meaning of unknown words based on the meaning of each part. data collection involved administering an etymology test among 60 male & female participants of age range 20-30. tests were administered both before and after the procedure in both control and experimental groups. data analysis of this study displayed that teaching of etymology strategy reinforce vocabulary learning of participants in experimental group. key words: etymology strategy, vocabulary learning.