The study investigates how Chinese English-as-a-foreign-language (EFL) learners construct translanguaging space via multimodal orchestration in collaborative English-language YouTube videos introducing Chinese culture. By triangulating multimodal analysis of videos and students’ interview responses, the current research maps translanguaging space construction within and across modes and identifies four multimodal translanguaging space patterns. Meanwhile, learners’ understanding of modal affordances, their intents, their perceptions of the intended audience, and their experiences with relevant (multimodal) texts were found to influence their multimodal orchestration in translanguaging space construction. Digital multimodal composing (DMC) provides EFL learners with opportunities to draw upon their expanded multimodal repertoires, to combine multiple modes for meaning-making creatively, and to transcend the boundaries of languages and modalities critically. Pedagogical suggestions are provided regarding integrating DMC tasks into multilingual learning environments.