The evolving nature of intercultural education necessitates a shift from static to reflective pedagogies among teachers. This case study investigates the efficacy of a collaborative lesson study (LS) approach in enhancing Chinese university instructors' proficiency in participatory, non-essentialist intercultural teaching. Six English as a Foreign Language instructors at a Chinese university engaged in three iterative LS cycles over one month, integrating new intercultural communication materials into their classes. Data were collected through lesson documents, observations, discussions, and interviews. The immersive LS process significantly expanded instructors' understanding of key intercultural communication concepts, encouraged the adoption of more student-centered methodologies, and prompted critical reflection on prior cultural assumptions. The collaborative engagement facilitated a deeper theoretical grasp and practical application of non-essentialist principles. Challenges included time constraints due to teaching workloads, discomfort in peer feedback exchange, and a broader lack of coordinated intercultural teacher training. Despite these challenges, this study underscores the potential of LS as a robust model for advancing intercultural teaching capacity through collaborative inquiry. It hints at the promise of LS in bridging the theory-practice divide in intercultural education, paving the way for more nuanced, non-essentialist instruction.