A finite element model was developed in this research to investigate the impact of defects on the mechanical properties of a 3D-printed composite sandwich panel that could occur during the layer alteration period between the dissimilar materials, affecting the interfacial strength between the layers and causing the 3D-printed panel to fail. Numerous parameters, such as interfacial position, size, material properties, and location of defects along the panel, have been examined that might affect the failure mechanism. This finite element study adopted linear elastic behavior by utilizing ANSYS simulation program. The outcomes showed that the midsection of the composite is under a lot of stress, and as we approach the edges of the composite, the tension concentration falls outward until it reaches zero. In the intact scenario, the deformation was zero at either end of the panel and highest in the composite middle. The shear stress was most significant in the center, and it decreased as we moved closer to the extremities of both sides, it gradually decreased until it was lowest there. The endpoints where we have support responses have significant maximum shear stresses, which could degrade the material overall mechanical properties. This rise in the maximum principle stress at the end support could be due to the reaction of the fixed support, which tries to counteract the applied flexural load and raise the maximum principle stress.