Abstract: The firearms manufacturing industry has investigated replacing firearms frames with lightweight materials, such as polymer, in recent years. This kind of innovation in the manufacturing industry can help the users be more comfortable and reduce possible injuries. Using additive manufacturing or 3D printing, prototyping the firearms' frame made of polymer is possible. Additive manufacturing uses a 2-dimensional layer fabrication approach to form almost any 3-dimensional object. However, there are no studies published yet regarding the performance of the firearms frames made of polymer. In addition, supporting studies regarding the capability to withstand the pressure and stress from the blowback and recoil process should also be done. To solve the gap, this study investigates the stress and deformation of a 3D-printed pistol frame made of polymer using Finite Element Analysis (FEA). A comparison between steel and polymer frame materials is also analyzed to show its performance. The analysis results revealed that changing the frame's material to polymer will decrease the weight by 51.73%. The resulting stress is slightly comparable for both materials but with an increase in the displacement due to recoil. The study is expected to provide valuable theoretical references for the design. Employing better structure, other curves, and increasing the thickness are recommended to remove the high concentration of stress on some model areas.