AbstractIn this work, resistance welding of a glass fiber‐reinforced epoxy composite (GFRC) was studied with numerical optimization and experimental validation. A steel mesh and polymethyl methacrylate (PMMA) films were used as the heating element and adherent interlayers, respectively. A transient heat transfer module was implemented to conduct the parametric optimization study, with variables of electricity power, clamping distance and weld time. The optimal welding condition was then confirmed as 20 W, 0.4 mm and 30 s, with a melting degree of 95.2%. A thermal meter and a thermal camera validated the simulated temperature results. Welding quality was experimentally characterized by single lap shear tests and scanning electron microscopy (SEM). The highest lap shear strength of 3.8 ± 0.3 MPa was captured on the specimen welded with the optimized condition. This was 76% that of the benchmark made with the adhesive bonding method but it was over 200 times faster.Highlights Resistance welding of GFRC with PMMA films and a steel mesh is studied with FEA. Simulation results are quantitatively validated with experimental methods. Optimal welding conditions are confirmed in association with welding tests.