Abstarct: Today, there are numerous concrete structures in the world that have been built several decades ago. These structures have been damaged throughout their lives. One of the available solutions is the destruction of existing structures, which has no logical justification due to high economical costs and environmental degradation. Another solution is to use different methods of strengthening existing structures. One of these methods is the use of engineered cementitious composites in structural strengthening. Engineered cementitious composite is an advanced type of fiber reinforced cementitious composites with high tensile strain capacity which is owed to the strain hardening and multiple microcracking. The advantage of using engineered cementitious composite in the structures is that it exhibits a considerable ductility. Although, many laboratory studies have already been done on engineered cementitious composite, only a few studies have been conducted on numerical modeling of engineered cementitious composite. The purpose of this study is to study the potential advantages of using engineered cementitious composite in beam strengthening employing finite element method. Therefore, a retrofitted beam with strain hardening cementitious composite was investigated. The use of strain hardening cementitious composite in different thicknesses was evaluated. For the abovementioned purpose, and for simulating the beam in a four-point bending test, a numerical model was created using Abaqus software and the available experimental results were used to verify the model. Finally, a parametric study was conducted on the factors affecting the resistance of the beam. The results have shown that increasing the thickness of the retrofitting laxyer, for a specific reinforcement ratio, leads to increment of the maximum bearable force on the beam.