Bilingual teachers' willingness to communicate (WTC) in a second or foreign language (L2) plays a crucial role in the effectiveness of bilingual education. Most research on L2 WTC has focused on L2 learners and language teachers, leaving a considerable gap regarding L2 WTC among subject teachers. This study investigated bilingual subject teachers' WTC in English and whether or to what extent anxiety and self-perceived communication competence are associated with teachers' WTC in English in the bilingual classroom. Three groups of bilingual subject teachers were surveyed: senior high (n = 41), junior high (n = 58), and elementary school teachers (n = 40). The results indicated that bilingual subject teachers had moderate WTC in English. All three groups' WTC was positively correlated with communicative competence and negatively correlated with anxiety. Anxiety and self-perceived communicative competence were powerful predictors of the elementary school teachers' WTC but were not significant predictors of the senior and junior high school teachers' WTC. Detailed analyses of the participants' interviews demonstrated that personal and socio-educational variables (i.e., language-related concerns and exam-driven academic culture) and contextual (i.e., students' English proficiency, comprehension, and feedback; lack of bilingual textbooks; and subject difficulty) variables influenced the bilingual teachers' WTC in English.