In recent years, the Indonesian government has put greater emphasis on promoting critical thinking in the education system, including the notion of critical thinking in national examinations, curriculum, and graduate outcomes for school education. Nevertheless, as in many testing-oriented countries, fostering critical thinking in the Indonesian context can be challenging, as the long-standing culture of testing, in which every answer is either correct or not, contradicts the concept of critical thinking. This paper focuses on identifying challenges in promoting critical thinking in English Language Teaching, especially in testing-oriented countries. The paper argues that critical thinking can be effectively fostered in students if teachers have a profound understanding of the notion. Demonstrating how critical thinking can be incorporated into teachers' daily pedagogical activities and encouraging teachers to conduct collaborative action research about the teaching of critical thinking are suggested as two productive ways to boost teachers' understanding of the notion of critical thinking.