Many studies have explored educational and pedagogical affordances of social media, but few studies have investigated their impact on emotional and psychological aspects of language learning specifically Willingness to Communicate (WTC) in second and foreign language learners. In this paper, we have reviewed related research published in the last decade and inspected their results and the researchers' points of view towards this issue. The main purpose of this study was to review the published papers to know about their data collection methods, contexts, participants, and predictors of WTC that were modified by social media. The findings showed that most of the studies utilized quantitative research design and were conducted in formal contexts in Asia. Social Media Assisted Language Learning (SMALL) users were often adolescent and young adult learners. Moreover, through analyzing data taking a content analysis approach, three themes related to predictors of WTC emerged: 1) SMALL and L2 learners' self-confidence, 2) SMALL and L2 learners' motivation, 3) SMALL and L2 learners' anxiety. The themes were examined in-depth and some interesting and remarkable studies were narrated thoroughly. Scrutinizing the themes revealed that social media helped language learners to improve L2 WTC by increasing self-confidence and motivation and decreasing anxiety. Based on the results, we recommend that researchers examine other predictors of willingness to communicate that can be modified by the aid of SMALL (e.g., intergroup climate or motivation). Furthermore, instructors can employ social media as effective teaching tools to enhance learners' communication competence and increase their participation in in-class activities.