Explosives are a group of special-purpose materials that are widely used in various branches of industry. Interest in this type of materials has increased recently in last years, especially due to the current geopolitical situation. Unique properties of explosives cause that they are often used against military personnel, citizens or critical infrastructure. Due to the high risk of attack using explosives, there is a great need to determine the threats associated with it. Performing an experimental research is related with high costs. Therefore, researchers are increasingly deciding to use numerical methods. In this paper results of numerical research evaluating the influence of deflector geometry on reducing the negative impact of a 4 kg TNT charge explosion on a pipeline is presented. During the research four different cases were analyzed. The research was carried out using the arbitrary Lagrangian–Eulerian method. Obtained results shown that the use of a deflector significantly reduces the negative impact of the blast wave generated by the TNT detonation. In the case of a pipeline without an additional deflector, the fracture of the pipeline was observed. In all cases where the deflector was used, there was no fracture of the pipeline however the plastic deformation is various depends from the deflector geometry. The use of deflectors with cone-like geometries reduced the negative impact of the blast wave on the analyzed pipeline to the greatest extent.