This research aimed to assess the quality of arguments and informal reasoning abilities of pre-service science teachers concerning various socio-scientific issues (SSI), utilizing dilemma cards. The case study method, a qualitative research approach, was employed, involving 12 pre-service science teachers. Participants completed the dilemma cards over a 12-week period. The analytical procedure for these cards incorporated content analysis. Findings from the study indicated that participants were often unable to construct a comprehensive argument that considered all argumentative components, such as claim, evidence, support, and rebuttal. While some participants displayed a modicum of success in the components of claim, evidence, and support, they typically provided insubstantial examples in the rebuttal dimension. On examining the nature of arguments based on context, it was discerned that the quality of arguments about nuclear energy differed slightly from those about other SSI. Nevertheless, context did not significantly influence the quality of arguments for 11 other socio-scientific topics. Furthermore, the study noted variations in the dimensions of informal reasoning across different SSI. It was subsequently inferred that the context might influence informal reasoning. In addition, it was observed that participants tended to focus more on the ecological dimensions of informal reasoning and less on the ethical-aesthetic dimensions. Recommendations were put forth to enhance both the quality of arguments and informal reasoning abilities.