Globalization and internationalization in higher education have promoted the worldwide popularity of English-medium instruction (EMI) programs. The successful implementation of EMI programs calls for content-language integration, which requires EMI teachers' language awareness. Yet, empirical studies investigating EMI teachers' language awareness still remains scarce. This study aimed to explore the development of language awareness through a Chinese EMI teacher's 10-month team teaching with an English teacher. With data mainly gathered from semi-structured retrospective interviews and video-recorded classroom observation, the study found that the EMI teacher experienced noticeable changes in language awareness and pedagogical practice. This study also yielded some important implications for EMI teacher education.