Social media is becoming a more active and accessible medium for learners all around the world to acquire the English language. A growing body of study is examining how people learn and use language in the digital age, and one such area of study is social media-based English language learning. This systematic review of the literature aims to provide an overview of social media, specifically WhatsApp, as a tool for learning English writing skills in existing literature. This review maps the experiences of learners with learning outcomes related to writing skills as they relate to WhatsApp. To examine the literature that was accessible for the study, a systematic review was conducted. This systematic review complies with the statement of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards. The review procedure included a thorough search of electronic databases like Web of Science, Google Scholar, Science Direct, and Scopus. The research articles, which were published between 2013 and 2022 were included in the search. The purpose of this systematic research is to investigate WhatsApp Messenger’s potential to help undergraduate EFL learners improve their writing skills. The review gives a summary of the body of research on the use of WhatsApp for writing instruction, including studies examining the app’s possible benefits for undergraduate EFL learners’ writing skills. Out of n = 90 research studies n = 20 research studies met the inclusion criteria for this systematic review. Among all those 20 studies, researchers adopted (n = 13; 65%) quantitative research methodology. According to the results of this systematic review, WhatsApp gained popularity among researchers in 2019 and 2021, and at that time, there were more studies conducted. The country-wise context of the research studies revealed that Saudi Arabia (n = 4; 20%) has made a significant contribution to the body of studies in which it was discovered that WhatsApp is a highly useful learning tool for improving the writing abilities of undergraduate EFL learners. Future research should explore WhatsApp’s impact on enhancing English writing skills among undergraduate EFL learners, considering diverse contexts and instructional strategies. Educators are encouraged to integrate WhatsApp for group projects, create engaging online environments, and continuously assess teaching methods. Additionally, research could investigate educators’ perspectives on WhatsApp-based approaches and explore the role of other social media tools, like Instagram, YouTube, and Facebook, in enhancing various English language skills.