The aim of the present study was to examine the role of teachers' attitudes and beliefs in the implementation of communicative language teaching (CLT) in Cambodian universities. It has repeatedly been demonstrated in past research to teach English for socio-economic, socio-cultural, and other pragmatic purposes in Cambodia. This research explored teachers' attitudes and beliefs toward the implementation of CLT using quantitative methodology. This research was carried out at public and private universities offering the undergraduate program in TESOL/TEFL. The data was collected from 358 teachers who were working in public and private universities. The results of the study showed that teachers' attitudes and beliefs are significantly related to the behaviours in the implementation of CLT in Cambodian universities. The findings concluded that teachers' attitudes and beliefs in managing their instructional practices have significant role in implementing CLT. In order to successfully implement CLT, they need to determine their individual attitudes, beliefs and behaviours. The current study is one of its own kind. To the best of the current study's author's knowledge, no such study has been conducted before.