This paper examines why communicative language teaching (CLT) fails to improve student learning in certain contexts by assessing two adult educators' communicative and noncommunicative practices through qualitative case studies, interviews, and participant observations. Results show no inherent CLT problems that prevent teachers from grasping CLT theory and transforming it into classroom practices. Communicative classroom practices lead to significant improvements in student communicative competence and four skills, whereas noncommunicative practices bring about poor student learning outcomes. Moreover, noncommunicative teaching incurs negative consequences for teachers and students more than traditional pattern-drill instruction. The study points to the teachers for CLT failures in certain contexts and recommends CLT to underpin English as a foreign language/English as a second language (EFL/ESL) curriculum and instruction, alongside changes in adult educator preparation programs and in-service teacher training. To avoid noncommunicative instruction, policymakers and initial and in-service teacher training programs should offer communicative training that mixes and balances theory and practice, and should monitor teacher cognition and behavior in actual classrooms.