The current study was an attempt to investigate the effect of graphic organizer strategy on improving Iranian EFL learners' vocabulary learning. Vocabulary knowledge has essential role in learning and using a language. Vocabulary is basic access to language, and is the main point to learn a language but language beginners are not so good in using methods that are useful to them in memorizing the words. It is so important how many words you know in speaking or writing or reading in a foreign or second language Graphic Organizer is a visual and graphic display that depicts information in various ways. Regarding the advantages of the Graphic Organizers it is worth mentioning that through making use of them as instructional tool: Content would be easier to understand and to learn, there is reduced information processing demand, and Students become more strategic learners. 50 students participated in this quasi-experimental study which lasted for one academic semester. University of Tabriz,College of Mizan Tabriz, Tabriz,Iran.