Informed by a combined framework of 'translanguaging' and 'epistemic injustice', this paper examines how a group of teachers and students from diverse linguistic and cultural backgrounds negotiated their knowledge participation through translanguaging in an English medium instruction (EMI) degree program at a Chinese university. Data were collected over a 12-month classroom ethnography, including lesson recordings, stimulated recalls, and reflexive journals. A thematic analysis of the data reveals that transnational teachers and students actively employed translanguaging to challenge the prevailing hegemony of Western thinking and knowing in the EMI environment. We identified three key translanguaging capacities that facilitated transformative knowledge negotiation: (1) counteracting testimonial injustice; (2) providing hermeneutical resources; and (3) enhancing the sensitivity of trans-epistemic practices. Our study attests to the value of translanguaging as a transformative strategy to generate epistemic access for transnational students engaged in EMI learning, informing efforts to foster educational equity in the internationalization of higher education and to empower transnational teachers and students to reclaim their epistemic contribution capacities in the EMI context.