This study investigated the effect of design thinking-based instruction on the writing performance, creative thinking skills, and writing motivation of second-year university students in the department of management. A quasi-experimental pretest-posttest control group design was employed. For this purpose, 51 students were randomly assigned from two intact classes in a university where 24 students of a class were randomly assigned as the experimental group receiving design thinking instruction, and 27 students of the other class were assigned as the comparison group receiving conventional methods. Data were collected through pre- and post- tests, as well as text analysis and students‘ reflective journals. While thematic analysis was employed to analyze the qualitative data, independent and paired sample t-tests were used to analyze the quantitative data. The results have revealed that the mean score differences between the experimental (M=4.90, 4.70, 3.92) and comparison group (M=2.65, 1.67, 1.84) on students‘ argumentative essay writing performance, creative thinking skills, and motivation to write, respectively. These differences are statistically significant between the two groups in essay writing performance, creative thinking skills, and motivation, with the mean of the experimental group being significantly higher than the mean of the comparison group at (t = 20.89, df = 37.09; t = 37.84, df = 38.86; t=40.94, df=41.93, p < 0.05) respectively. Particularly, the experimental group of students‘ writing performance and creative thinking skills achieved higher scores in task achievement, coherence and cohesion, lexical resources, grammatical range and accuracy, and fluency, flexibility, elaboration, and originality than the comparison group. Based on the findings, it is possible to conclude that design thinking-based instruction significantly enhanced the students‘ argumentative essay writing performance, creative thinking skills, and writing motivation. Finally, implications for teachers, researchers, educators, course book writers, and policymakers have been forwarded to consider employing the design thinking method to promote effective essay writing, creative thinking skills, and motivation in the field of English language teaching.