The primary purpose of the present study was to examine the effects of explicit text structure instruction on the expository text writing of grade seven EFL students in Debre Markos City, Amhara Region, Ethiopia. Using a quasi-experimental research design, two intact groups of learners were randomly selected from two government schools, Dibza and Biruh Tesfa Primary Schools, and assigned as the treatment (n = 44) and control (n = 39) groups, respectively. The participants in the experimental group received explicit text structure instruction in two phases. In contrast, the participants in the control group followed the conventional instruction provided in the curriculum. The required data were collected through tests and classroom observations and analyzed using quantitative methods. Independent samples t-tests were used to analyze pre-test data while analysis of covariance (ANCOVA) and percentages were used for the posttest data. The results from the independent samples t-test showed that the two groups did not exhibit significant differences across all study variables. However, by controlling for the pretest scores, the analysis of the posttest data using ANCOVA revealed that the experimental group achieved statistically significantly higher results than the control group in text structure identification (p < .001, η² = 0.34), simple descriptive paragraph writing (p < .001, η² = 0.28), and cause-and-effect paragraph writing (p < .001, η² = 0.37), with large effect sizes. An analysis of the participants’ texts also revealed that the experimental group surpassed the control group in the inclusion of main ideas and supporting details, as well as in word choice, in their simple descriptive (p < .001, η² = 0.57; p < .05, η² = 0.07) and cause-and-effect paragraphs (p < .001, η² = 0.43; p < .001, η² = 0.35), with medium to large effect sizes. Substantial improvements were also observed in the topic sentence quality of their simple descriptive paragraphs (p < .05), with a medium effect size (η² = 0.06). Moreover, the study revealed that the groups significantly differed in their posttest scores for transition word use (p < .05), with a medium effect size (η² = 0.07). Based on these results, it can be concluded that explicit text structure instruction is highly effective in improving grade seven EFL students’ expository text writing. In light of the findings, it is recommended that future studies focus on all expository text structures or those not covered in the present study and investigate the efficacy of TSI on students' expository writing in wider and more diverse contexts, such as different sample sizes, grade levels, school facilities, and locations. Furthermore, practical applications of the findings are directed to curriculum developers, textbook writers, and English teachers.