The usefulness of theory in interpreter training is widely recognized. Yet descriptive studies on which theories are used and how they are pedagogically treated in training are scant. This study aims at investigating which theories are covered and how they are pedagogically treated in interpreting textbooks. Content analysis was used to code 58 interpreting textbooks against a theory category framework for coverage. The results indicate that 14 theories and 33 categories of insights from the literature are covered in the textbooks. The two most popular theories are the Effort Model and Interpretive Theory, while the highly covered categories of insights from the literature concern the component skills of interpreting. Textbooks that cover the two most popular theories were coded against a pedagogical treatment framework. The results suggest that, although the theories are adequately treated in language presentation and information amount, they are poorly discussed in relation to practice, indicating that the textbooks fail to create situations for students to construct meaningful knowledge of theories from their own interpreting experiences, which is close to a transmissionist approach. Possible reasons for the two theories’ popularity and the impact of a transmissionist approach are discussed against the current literature.