The current study aims to investigate L2 students' writing performance in mobile-assisted flipped learning. The participants were 45 first-year university students in in Seoul, Korea. They were enrolled in a 2-credit English course that met once a week for two hours. During one semester, the mobile-assisted flipped learning was implented, and four-integrated language skills with focus on writing were taught. The participants' average seat time and scores were recorded in the mobile application to measure their participation. In total, 45 complete sets of second and the sixth assignments were collected and anlayzed both quantitatively and qualitatively. For the quantitative results, two raters evaluated using ACTFL Proficiency Guidelines 2012. For the detailed text analysis including metadiscourse comparisons by participation level – high, moderate, low – were conducted using an online text analysis tool, Text Inspector. Major findings of the study shows that mobile-assisted flipped learning has a significantly positive impact on L2 writing, and it was found that students' participation levels in mobile-assisted flipped learning was positively related with the number of metadiscourse markers used. Based on the findings, suggestions and implications are provided.