Problem-based learning (PBL) has been widely incorporated in STEM classrooms. Unfortunately, its effectiveness for foreign language teaching is less explored. This design case describes the design and implementation process of a Chinese PBL unit in a US elementary school along with the design considerations of teaching dilemma-centered instruction. We provide detailed accounts of our process of developing this PBL curriculum, learning materials, and the two rounds of implementations. We also reflected on the design process and examined the design dilemmas faced by this interdisciplinary design team. Findings show multiple design tensions, which include balancing the language and PBL teaching goals, balancing L1 and L2 use, and the communication challenges within a collaborative design project.