Because of its importance to university students, writing is a skill that students need to develop and improve to pursue their studies and research tasks that are required of them by their disciplines. However, many university students face problems when it comes to producing effective written works. This problem could be attributed to the poor mastery of grammar by students and their inability to produce correct sentences. In this regard, our study aims to investigate the effects of a proposed model of grammar teaching, which is the integrative grammar teaching method (IGM), on developing students' writing performances. To carry out this investigation, we opted for a Mixed-methods research approach applying a Case Study and a Quasi-experiential research strategy. Four questionnaires, a test, and observation were the main data collection methods we used in this study. The analysis and interpretation of the collected data revealed that IGM could help students develop their writing performance.