In this paper, the content knowledge and pedagogical content knowledge of teachers of Latin as a foreign language are modelled and examined using a convenience sample (N = 216) with newly validated test instruments. Bivariate correlations show significant relationships between domain-specific professional knowledge and indicators of school or academic success, but no relationships with professional experience. In a confirmatory factor analysis, the two categories of knowledge can be separated according to theory. Their correlation is lower among in-service teachers than pre-service teachers, as multigroup analyses suggest. Furthermore, in-service teachers have more content knowledge and pedagogical content knowledge than pre-service teachers.