Getting students to act out their roles and to apply appropriate arguments for and against their position as defined by the role is a challenge in approaching and exploring an environmental issue through role-playing. This action research addressed this concern by exploring how a semi-scripted role play could be used to promote active student learning in a Science, Technology and Society (STS) lesson. Using greenhouse effect as an example of environmental issue, this study explored how students playing different characters articulated their response to the semi-scripted role play setting. A group of 26 master students who took Science, Technology and Society (STS) as a core course took part in research and carried out a role play in groups of six for a period of two hours. The multiple data sources for this study consisted of student’s written reflections, an informal and unstructured observation, and Role Play Evaluation Form. Overall, the students indicated that the semi-scripted role play helped them understand an environmental issue both from their own and other’s perspective. The provision of guiding information via semi-script enabled students to feel empowered to express, share, argue, and negotiate more comfortably and confidently. In addition, students indicated that the role play helped them to develop critical thinking. The role play had helped create an engaging and productive learning experience that educators could use this exercise to lead students in the exploration of broader local environmental issues.