With the growing importance of English communication competence in global communications and English learning, willingness to communicate (WTC) has received attention as a predictor of students’ participation in communicative learning activities. Research on L2 WTC has reported causal relations between L2 WTC and personal and situational factors including motivation, perceived competence, L2 anxiety, and classroom environment. This study examined a hypothesized structural model of causal relations between L1 WTC, L2 communication competence, intrinsic language learning motivation, L2 speaking anxiety, classroom environment‒teacher support, task orientation, and peer support‒ and L2 WTC. A total of 1,277 college and secondary students participated in a survey. The data were analyzed to examine a structural equation model of L2 WTC in EFL class in Korea. Analysis procedures included exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and estimation of structural equation modeling (SEM). The results evidenced the fitness of the hypothesized SEM. The findings confirmed casual relationships between latent variables in the model. Direct effects of motivation, perceived competence, and L1 WTC were significant on L2 WTC. Indirect causation was also found to be significant. L2 anxiety had a negative indirect effect on L2 WTC, mediated by competence. Classroom environment affected L2 WTC through motivation and competence. Motivation significantly influenced L2 WTC both directly and indirectly. Discussions on research results and implications and limitations of the study are presented.