The purpose of this paper is to present an appraisal of a lesson-study implementation with pre-service biology teachers concerning a health education issue, how blood pressure works and how it is affected. The participants were 11 pre-service teachers, a secondary school biology teacher and three teacher educators from a local University. A qualitative and interpretative approach was followed. Data were collected through participant observation, content analysis of the pre-service biology teachers' individual written reflections, and their proposal of a lesson plan. The results evidenced the value of this formative approach, concerning the learning opportunities it offers, not only related to the scientific content knowledge but also the didactic knowledge developed by pre-service teachers. They seemed to develop a holistic understanding of how to teach a theme as multidimensional as this one, health education, but they also developed didactic knowledge related to different central aspects of the teaching process, concerning lesson planning, task development, classroom management, and communication, and became aware of the importance of developing several crucial competencies as science teachers. The lesson-study approach revealed to be a strategy for learning about teaching planning that has the particularity of bringing theory and practice remarkably closer.