Mobile phones as new addition to information and communication technologies have created new ways to help learners in the process of foreign language learning. Given the importance of vocabularies for EFL learners, this study was an attempt to investigate the effectiveness of short messaging (SMS) via social networks on Iranian Upper-Intermediate EFL learners' vocabulary learning and retention. To this end, sixty university freshman students with upper intermediate proficiency level were chosen

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... to take part in this study, 30 as control and 30 as treatment group. During 16 weeks of experiment, half an hour of the class time of each group was attributed to working on the book 504 words. At the end, both groups were given a teacher-made vocabulary test from 504 absolutely essential words, to see the effect of SMS on their vocabulary learning and the scores of each group were compared employing an independent t-test. The result of the t-test showed that both groups had improved in the post-test. Although there was not any significant difference between the groups in the post-test, the result of the delayed post-test showed that SMS via social networks had more significant effect on vocabulary retention compared to using traditional ways such as dictionary definitions, and the experimental group outperformed the control group.