The purpose of this study was to explore translanguaging space as a transformative third space, where alternative and competing discourses are celebrated and where science learning and the development of science's discourse and epistemic practices expand across overlapping boundaries (e.g., home, school, and community). The study focused on Syrian refugee youth adapting to learning science in English in the Lebanese multilingual educational system that esteems international languages (English or French) over Arabic. Our research questions included: (1) What translanguaging practices and functions emerge during a linguistically responsive life science unit designed for refugee multilingual learners? (2) How does a translanguaging space act as a third space for refugee learners to engage in meaning-making and science practices and discourse around the topic of "respiration"? The study utilized a qualitative instrumental case-study approach to generate data around refugee learners' languaging practices and their development of science understandings, practices, and discourse. We also engaged in participatory methodologies that challenge boundaries between researchers and participants. The data sources were 22 Zoom recordings, students' work, and participant-generated feedback. Thematic analysis was used to analyze transcripts and students' work while adhering to trustworthiness criteria. Our findings center translanguaging as a justice-oriented pedagogy that enables a productive and "inviting" third space for refugee multilingual learners to make meaning of phenomena by bringing together and extending their semiotic and epistemic repertoires. Serving multi-tiered functions, translanguaging fostered dialogic connections that affirmed students' "outside" social spaces as valuable resources for meaning-making in science classrooms. The implications discuss design features that support a fluid and purposeful translanguaging third space for asset-oriented science learning.