Purpose: The purpose of this study was to assess the quality of scientific arguments developed by pre-service physics teachers.Sample: The participants were 171 pre-service physics teachers recruited from two universities: 86 from University A and 85 from University B.Design and method: Participants were prompted to develop a written argument to either support or challenge the Turkish government's decision to invest in nuclear power plants. Data consist of written arguments developed by the participants and information on participants' knowledge of the topic, their confidence in their knowledge and the source of their knowledge related to the topic. Data were analyzed using the CER framework.Results: The results show that participants did not perform at the expected level. The majority of students failed to develop strong scientific arguments. While almost all of the participants provided evidence to justify their claims, they failed to effectively coordinate evidence, claim and theory to develop an argument. Students struggled the most in the warrant/reasoning category of the CER framework. We also identified several misconceptions that students held related to nuclear power plants.Conclusions: In our discussion we problematize college science teaching and advocate integration of instructional strategies such as argumentation that can effectively engage students in construction, evaluation and justification of knowledge.