The ability to build arguments is a crucial skill and a central educational goal in all school subjects including science as it enables students to formulate reasoned opinions and thus to cope with the increasing complexity of knowledge. In the present cross-sectional study, we examined the domain-specificity of argumentative writing in science by comparing it with a rather general type of argumentation as promoted in first-language education and with formal reasoning to gain insight into different forms of argumentation on theoretical and empirical levels. Using a paper-and-pencil test, we analyzed written argumentations and the reasoning abilities of 3,274 Grade-10 students in German secondary schools. Correlation and multiple regression analyses as well as a qualitative analysis of students' answers to a subset of tasks in the domains of science and first-language education were conducted. Results showed moderate relations between argumentation in science, argumentation in first-language education, and reasoning. Half of the variance in argumentation in science was explained by individual differences in argumentation in first-language education and reasoning. Furthermore, the examination of written arguments revealed differences, for example, in students' weighing of pros and cons. We assume that the familiarity of the underlying scientific information may play an essential role in the argumentation process and posit that it needs to be investigated in more detail. Overall, the study indicates that investigating the argumentational abilities of learners in first-language education and reasoning abilities can help to shed light on the domain-specificity of argumentation in science.