Reading comprehension and vocabulary knowledge have critical roles in success in a foreign language. They have also intricate relationships so that the increase in one leads to increase of the other. The aim of the present study was to investigate the effect of learning vocabulary via SMS -as an optimal way of teaching words-on university students reading comprehension. To this end, 45 freshmen students took part in this study. They were assigned as experimental and control group. Before the beginning of the experiment both groups took a vocabulary test and a reading comprehension test. During 16 weeks of experiment the participants of the experimental group were taught 320 headwords of the Academic Word List (Coxhead, 2000) via SMS. The control group learned them by using a dictionary. Both groups were assessed each session by the instructor in the class. At the end, both groups were administered a reading comprehension test as a post-test. The result of the post-test showed that although there was not any difference between the two groups in the pre-test, the experimental group outperformed the control group in reading comprehension test (t = 2.31, P = .02). However, both groups had improved in the post-test regardless of the medium of learning. In addition, the participants of the experimental group filled out a questionnaire International Journal of Linguistics ISSN 1948-5425 2012 www.macrothink.org/ijl 276 regarding their attitudes towards SMS vocabulary learning. It was found that they had positive attitudes towards this approach of vocabulary learning. Based on this result, language teachers need to seek every opportunity to teach words to students to improve their reading comprehension. However, because of the superiority of SMS on other means of learning vocabulary, it is recommended that this approach of vocabulary learning be used to help students in the reading process.