Flipped classroom approaches have increasingly been adopted in the Australian higher education sector. However, current research on this approach is predominantly quantitative and focused on domestic students. Little is known about the flipped classroom learning experiences of undergraduate international students in Australia. This paper sets out to investigate undergraduate international students' challenges in a flipped classroom environment, based on thirty-two semi-structured interviews with undergraduate international students at an Australian university. We identified several challenges, including language issues, barriers to autonomous learning, as well as technical and technological challenges. International students in our study also provide constructive recommendations to improve the design of the flipped classroom. This paper contributes new insights into the nuances of undergraduate international students' challenges in a flipped classroom environment.