en Effect of MALL on the Acquisition of Receptive and Productive Knowledge of L2 Vocabulary by Iranian EFL Learners: The Case of Telegram تخصصي Special پژوهشي Research <span style="font-family:Times New Roman,serif;"><span style="font-size:10.0pt;">This study investigated the role of Telegram, a mobile messenger app, in mastering</span></span><span style="font-family:Times New Roman,serif;"><span style="font-size:10.0pt;"> receptive and productive knowledge of vocabulary by Iranian EFL learners. In addition, it was intended to survey EFL learners&rsquo; attitude toward using telegram to learn English vocabulary. Therefore, both quantitative and qualitative design were used. So, 57 students were selected from a language institute in Isfahan, Iran. To homogenize the participants, Oxford Quick Placement Test (OQPT) was administered and the participants were divided into two groups accordingly, a Telegram group and a control group. At the beginning of the study</span> a checklist of words was given to the participants. Afterward, during the study, the experimental group received the treatment (teaching words via telegram), while the control group received the target words traditionally. After 8 sessions, 20-30 minutes each, an achievement test was administered to the groups. The results of Independent Sample t-test revealed a statistically significant difference between the achievement test scores of the experimental and control group.</span> <span style="font-family:Times New Roman,serif;"><span style="font-size:10.0pt;">Moreover, the participants had positive attitude about using Telegram to learn English vocabulary. The findings of this study may inspire teachers to use mobile applications and also course developers to modify and improve not only the curriculum, but also the methodology of teaching vocabulary.</span></span> This study investigated the role of Telegram, a mobile messenger app, in mastering receptive and productive knowledge of vocabulary by Iranian EFL learners. In addition, it was intended to survey EFL learners&rsquo; attitude toward using telegram to learn English vocabulary. Therefore, both quantitative and qualitative design were used. So, 57 students were selected from a language institute in Isfahan, Iran. To homogenize the participants, Oxford Quick Placement Test (OQPT) was administered and the participants were divided into two groups accordingly, a Telegram group and a control group. At the beginning of the study a checklist of words was given to the participants. Afterward, during the study, the experimental group received the treatment (teaching words via telegram), while the control group received the target words traditionally. After 8 sessions, 20-30 minutes each, an achievement test was administered to the groups. The results of Independent Sample t-test revealed a statistically significant difference between the achievement test scores of the experimental and control group. Moreover, the participants had positive attitude about using Telegram to learn English vocabulary. The findings of this study may inspire teachers to use mobile applications and also course developers to modify and improve not only the curriculum, but also the methodology of teaching vocabulary. mobile application, productive vocabulary knowledge, receptive vocabulary knowledge, social networking sites (SNS), telegram mobile application, productive vocabulary knowledge, receptive vocabulary knowledge, Social Networking Sites (SNS), Telegram, 102 114 http://ijreeonline.com/browse.php?a_code=A-10-791-1&slc_lang=en&sid=1 Sepideh Mohammad sharifi Sepideh Mohammad sharifi mohammadsharifi2073@gmail.com 10031947532846002203 10031947532846002203 Yes Department of English, Shahreza Branch, Islamic Azad University, Shahreza, Iran Department of English, Shahreza Branch, Islamic Azad University, Shahreza, Iran Mohammad Ali Heidari Shahreza Mohammad Ali Heidari-Shahreza Heidari1387@gmail.com 10031947532846002204 10031947532846002204 No Department of English, Shahreza Branch, Islamic Azad University, Shahreza, Iran Department of English, Shahreza Branch, Islamic Azad University, Shahreza, Iran