In the goal of science teacher education, the role of reflection to cultivate the teacher as a transformative practitioner has been largely recognised. Reflective thinking is crucial for teachers to be mindfully and knowledgeably situated in teaching and transforming their actions. This study looks into the dilemmas of teaching practical work in elementary science classes and the roles of reflective thinking. Five preservice teachers, one inservice teacher, and one science teacher educator participated in the process of collaborative reflection (reflective writing on dilemma cases, sharing, and discussing) of teaching practical work during the preservice teachers' practicum. All participants wrote and shared two cases of his/her own dilemmas after teaching or observing lessons with science experiments. Preservice teachers also participated in a survey questionnaire and interviews to share their perspectives of practical work and the process of reflection. Looking into their reflection and discussion on the dilemmas of teaching through science practical work, the study attempts to explore how to make collaborative learning opportunities through reflective thinking. The findings of this study showed that the dilemmas of science practical work emerged in various dimensions of teachers' expectation and classroom interactions. Discussions on dilemma cases could facilitate reflecting and learning from different perspectives among participants. Based on these findings, we further discuss the implication of interactive reflection and discussion on dilemmas of practical work to enhance science teaching and develop collaborative communities in science teacher education. (Contains 2 tables and 1 figure.)