Critical thinking skills have been so far believed to be the solid background for learning a foreign language. Writing, which makes students analyze, think and successfully create products, surely needs indispensable critical thinking skills. Thus, applying critical thinking skills in English language teaching (ELT) is the content of this study. The current study aimed to explore the effectiveness of the teaching method applying critical thinking skills on the English majors at Ho Chi Minh City University of Social Sciences and Humanities (USSH) both improvement on the skills and attitudes toward the teaching method. With a quantitative mixed research, the study found that the teaching method actually improved students' essay writing ability when the paired-sample t-test stated that the difference between the assignment 1 score set, the pre-test, and the final exam score set, the post-test, was statistically significant with Cohen's d effect size of 0.18. The regression analysis statistically significantly resulted that students highly appreciated the teaching method with the strong effects were put on the global aspects of writing skills, Coherence and Cohesion, Organization and Task response in this study, but not on the surface aspects, Grammar and Sentence structure and Vocabulary. (193 words)