Socioscientific issues (SSIs), which are an important component of scientific literacy in science education, are scientific-based issues with dilemmas and no clear answers. SSIs can be local issues that affect a region or global issues that affect the world. This study aimed to investigate informal reasoning (IR) patterns and their influencing factors on science teachers about local SSIs. The research was designed as a case study. The participants consisted of 38 science teachers from various provinces of Central Anatolia, where the local features of context were at the forefront. Teachers were asked to form an IR about the texts with dilemmas addressed to them. Using content analysis, teachers' IR patterns were based on rationalistic, emotive, and intuitive reasoning; factors affecting their reasoning were analyzed according to sociology-culture, environment, economy, science, technology, ethics-morality, and policy (SEE-STEP). In the results, science teachers mostly use rationalistic IR and rationalistic and intuitive IR patterns about energy-related local SSIs. While the factors that most influence teachers' IR regarding local SSIs are economy and environment, the factor that least influences their IR is ethics. As a result of the study, IR is closely related to the context and environmental/socio-cultural background that can influence IR. Based on the result that teachers' IR is affected by the content, the main suggestion of this study is to investigate the IR of different contents in local SSIs.