The significance of this study is heightened by the fact that critical thinking (CT) is vastly seen as a major objective of higher education and the basis for the development of learning outcomes. Thus, this quasi-experimental aims at promoting and assessing students' critical thinking skills (CTSs) through argumentative essay-writing. It also investigates the correlation between CT and essay-writing skills. The main question addressed is: what is the effectiveness of promoting CTSs through argumentative essay-writing among English major students in terms of interpretation, analysis, evaluation, inference, and explanation? An instructional material was designed and implemented in classroom teaching to enhance CT. The study was conducted on 98 English major male participants enrolled in an essay-writing course at Prince Sattam bin Abdulaziz University (PSAU), Saudi Arabia. The participants were randomly assigned to either intervention (n =49) or control (n =49) groups. Quantitative-qualitative methods were employed. Pretest and posttest were applied to both groups. The Facione and Facione (1994) CT scoring rubric was utilized for assessing CTSs. Findings revealed that CT and essay-writing skills are significantly positively correlated. Assessment of students' essays denoted that the intervention group significantly surpassed the control in the five CTSs: "interpretation, analysis, evaluation, inference, and explanation" (Facione 1990, p. 8). It can be concluded that explicitly teaching CTSs through essay-writing can be effective in the development of these skills. The study recommended that further studies be implemented in different universities and also using other CT definitions and skills, and comparisons between the findings could be made.