Teachers' beliefs can be seen as psychological seeds planted in teachers' minds. Teachers' beliefs about effective inquiry-based teaching impact their intentions, instructional designs, and actions required for inquiry-based lessons. This paper discusses how to help Thai preservice science teachers who engaged in their student-teaching practicum in middle schools transform their beliefs toward inquiry-based science teaching through Lesson Study (LS). The research questions guiding this study include: 1) What critical factor contributes to Thai preservice science teachers' transforming their beliefs toward inquiry-based science teaching? 2) How could LS help Thai preservice science teachers transform their beliefs toward inquiry-based science teaching? and 3) How can LS be integrated into Thai preservice teacher education programs to cultivate preservice science teachers' inquiry-oriented beliefs and experiences in LS? Multiple data sets were collected, including teacher interviews, LS discussion meetings, and reflection forms. The cross-case analysis indicated that although all preservice science teachers developed more inquiry-oriented beliefs through the LS sessions, their progression paths varied among preservice teachers. A nonanxiety-driven facilitation and flexible modifications were found to be essential for making the LS sessions meet each preservice science teacher's idiosyncratic needs so that their belief transformations take place towards inquiry-based teaching as they overcome their fear and anxiety in adopting this approach. This study suggests that this facilitation is vital in unlocking diverse avenues of transformations in preservice science teachers' varying belief systems toward inquiry-driven science teaching.