The study aims to find out the effectiveness of I-Teach model to improve teachers' professionalism in handling special-needs children in inclusive classes. This is the final part of a research and development project with the modification of its development stage by Sukmadinata (2017) to be a model testing stage. It explained the effectiveness of the I-Teach model through a true experimental design by classifying the control and experimental group. The subjects of the study were purposively selected, with a total of 24 inclusive teachers involved. The study signified the effectiveness of the I-Teach model in facilitating the improvement of teachers' professionalism in managing inclusive classes. The effectiveness of the model has been confirmed through an Independent Sample T-Test between the control and experimental group, as sig = 0.000 < 0.05 and tcalc = -7.85 < -ttab = -2.074. The result of analysis confirmed the significance of the teachers' professionalism at the experimental group compared to the control group. The study recommended the provision of trainings for all teachers to equip them with sufficient comprehension of inclusive education and special-needs children management, as part of the sustainable improvement of their professionalism.