Translingual pedagogies have been proposed and implemented to respond to the increasing linguistic and cultural diversity in today's classrooms. However, the findings of translingual pedagogies on English as an additional language (EAL) writing vary from facilitating to undermining teaching and learning. To understand the empirical landscape of this young and fast-growing research area, I systematically reviewed 62 studies with a research synthesis method to explore what translingual activities have been implemented and how they have impacted EAL writing teaching and learning (including both K-12 and post-secondary contexts). The findings reveal that various translingual activities, such as self-reflective writing and literacy narrative, have been enacted in EAL writing teaching and learning. These activities have been practiced in different ways based on different rhetorical situations. The results show that translingual pedagogies can complement currently practiced EAL writing pedagogies, increase EAL student writers' awareness of English monolingualism, facilitate EAL writing teaching in different rhetorical situations, engage students in learning activities, and help view codemeshing as a matter of agency in EAL writing teaching and learning. Despite these benefits, there are some challenges to implementing translingual pedagogies, such as teachers' and students' concerns about codemeshing in high-stakes writing, the lack of teacher education and guidance in translingual pedagogies and practices, and the exclusion of some linguistically minoritized students. In sum, translingual pedagogies can enrich EAL writing teaching and learning, albeit with some challenges.