This study examined the mediating roles of two forms of willingness to communicate (WTC) in the relationship between teachers' attitudes toward classroom interaction and L2 classroom teaching behaviors. Classroom interaction is held to be pivotal in the acquisition of a second language, and the attitudes of L2 teachers toward it may play a critical role in determining their instructional willingness to integrate it into their teaching and the extent to which it features in their teaching behavior. However, few studies advance this line of research. To address the research gap on this issue, the purpose of this study is to establish an empirical model to examine the causal relationships between the attitudes of L2 teachers toward classroom interaction, their instructional willingness, and their teaching behavior. The empirical data consist of survey responses from 410 Taiwanese high school teachers of English. The structural equation modeling (SEM) results showed that both the general form and the instructional form of WTC significantly mediated the causal relationships between teachers' attitudes toward classroom interaction and teachers' L2 teaching behaviors. A multi-group analysis further showed that the two forms of WTC played a more salient mediating role in the practice of senior teachers, defined as those with more than 10 years of teaching experience, than in the practice of junior teachers, defined as those with 10 years or less teaching experience. The research and pedagogical implications are presented in light of the research findings.