The present study analyzed the structural and the content complexity of 76 preservice science teachers' socioscientific argumentation in the context of a mandatory COVID-19 vaccination. Data were analyzed within the methodological frame of qualitative content analysis. Concerning the structural complexity, the participants' socioscientific argumentation reached a relatively high level (i.e., justifications with elaborated grounds). Concerning the complexity of content, the sample referred to science-, ethics-, society-, and politics-related arguments (i.e., almost the full range of content areas); however, on an individual level, participants referred to merely an average of two content areas. Regarding the relationship between structural and content complexity, a significant positive correlation was found. In sum, the results of this study suggest that preservice science teachers' socioscientific argumentation is on a promisingly high level in terms of structural and on a medium level regarding content complexity. The findings are discussed and implications for science teacher education and assessment in science education are proposed.