This study introduced an instructional pattern that integrated the framework of the International Critical Thinking Reading and Writing Test (ICTRWT), designed by Paul and Elder, into a tertiary English as a Foreign Language (EFL) argumentative writing course. To measure the effects of the instructional pattern, a mixed methods approach was adopted. Two groups of students were involved in the experiment, with the treatment group receiving the instructional intervention and the control group receiving regular instruction in a tertiary argumentative writing course. A critical thinking test and a writing test were used to investigate the effects of the treatment, and questionnaires and interviews were also employed to examine students' attitudes toward the instructional pattern. The quantitative statistic data reveals that students who received the instructional treatment outperformed the students in the control group in terms of overall critical thinking skills and skills of identifying and evaluating the elements of thoughts. Meanwhile, the treatment group also performed better with regard to overall writing ability, organization and coherence. Additionally, the data gained from the questionnaires and interviews suggest students' general positive attitudes toward the instructional pattern.