Learning vocabulary is probably the most challenging and time-consuming part of learning a foreign language. Researchers argue that social media could affect learners' vocabulary acquisition. It is hypothesized that teaching science concepts could accompany vocabulary acquisition. We investigated the possible role of social networks (i.e. Telegram) in the improvement of vocabulary knowledge among undergraduate students from the Iranian University of Medical Sciences during September and October 2017. We conducted a quasi-experimental controlled before-after study and allocated female students to intervention and comparison groups at their academic major level (32 public health students as intervention, vs. 29 subject from nutritional sciences as a comparison). The intervention and comparison groups attended 6 lectures. The learners in the intervention group received additional video and text material through Telegram on a weekly basis and we had an open discussion regarding the important word and concepts. Students in both conditions were given a pretest at the beginning and a posttest at the end to measure growth in vocabulary acquisition. We used a linear regression model, adjusted for concept score, pre-test vocabulary score, lecture attended, education and marital status with pretest scores serving as a covariate. We have investigated 61 subjects, where, 32 participated in the Telegram group discussion related to the science concept. Six standard educational videos delivered through a filmed lecture distributed among the intervention group, each of which was approximately 500 words (ranging from 450 to 707) long. We have observed significant improvement in the vocabulary score of participant in intervention (before = 34.37 vs after = 46.03) and comparison groups (before = 32.79 vs after = 36.31). However, the intervention group significantly outperformed the comparison group, P < 0.05). the current study showed that online collaborative learning (i.e. using Telegram), as an assistance tool in education, can increase the communication between teaching faculty and students in such a way that resulted in significant improvement in the vocabulary score of SLL.