The purpose of this study was to analyze the potentialities of a learning module, created within an Erasmus+ project, which involved pre-service elementary teachers in a socio-scientific scenario related to green cities. The participants were involved in a panel discussion activity, with the main objective of discussing and reflecting on how to transform a particular city into a green city, taking into account the perspectives of the different stakeholders. A total of 60 pre-service teachers and one teacher educator were involved. In this case study, data were collected through a pre- and post-questionnaire, on the importance of a set of transversal skills at a professional and personal level, two focus-group interviews, and a panel discussion analysis. The results revealed that this activity has the potential to promote pre-service teachers' competence to assume a holistic view of an environmental issue, contributing to the development of their capacity to make "justified decision-making." It also allowed pre-service teachers to experience and reflect on new visions of science education from a learner's perspective. These outcomings are extremely important for helping pre-service teachers to create innovative learning contexts capable of promoting more critical, responsible, and pro-environmental active citizens.