Research on translanguaging in applied linguistics and language education is on the rise, and translanguaging application in English as a foreign language (EFL) writing programs has aroused great interest. Research on translanguaging practices testifies to the benefits of deploying multilingual, multimodal, multisemiotic and multisensory resources in multilingual classrooms, of which little presents the specific implementation and outcomes of translanguaging pedagogies applied in EFL writing education. In response, this ethnographic classroom-based research, one taking place in a comprehensive university in southwestern China, aims to explore the educational influence of translanguaging pedagogies particularly on learners' critical thinking, content comprehension and effective communication. To triangulate data types and sources, data-collection methods include e-questionnaires, classroom observations, audio-recorded interviews and student writing samples. Data analysis reveals that translanguaging practices, as part of the classroom writing ecology, promote EFL students' critical awareness. Additionally, translanguaging pedagogies facilitate students' content comprehension and effective communication. This study demonstrates the affordances of a translanguaging lens for EFL writing education provided that it is reframed to serve students' strategies to negotiate language differences.