Purpose: Despite numerous kinds of research regarding the potential of lesson study (LS) in internship and microteaching in teacher education curricula, studies examining the adaptation of LS in the lesson planning (LP) course have not been established. To fill this gap, this study aims to explore the perceptions of pre-service biology teachers of an adapted LS in the LP course toward their instructional design skills and teaching competency. Design/methodology/approach: This study opted for basic qualitative studies. The participants were eleven pre-service biology teachers in their third year who had already taken a LP course. Data were collected through semi-structured interviews. Collected data were then transcribed and thematically analyzed using grounded theory and focused on participants' perceptions about the development of their teaching competency in lesson planning through LS. Findings: The findings revealed that participants appreciated the planning and consultation phases, teaching practice, peer observation as well as observer feedback from the reflection phase in supporting the development of their basic teaching skills. There was also a change in their perceptions related to the concept of teaching. Originality/value: The findings of this study offer insight regarding the benefits and challenges of involving pre-service biology teacher students in the LS for biology teacher education programs with a focus on the method or LP course.