This study investigates the impact of CuO and TiO₂ nanoparticles (NPs) in polyvinyl chloride interface of ultrasonically welded glass fiber-reinforced plastic. Welding pressure, duration and holding time were optimized for superior mechanical bonding. Response surface methodology was employed to develop a regression model incorporating welding time, NP weight percentage and thermal conductivity. The results indicated that using a 2 bar pressure, a holding time of 0.5 s, 1 wt.% CuO, and a welding time of 0.45 s, the nanocomposite (NC) demonstrated its maximum breaking load of 2039 N. When the welding time was reduced to 0.4 s for the NC with 1 wt.% TiO₂, a slightly lower breaking load of 2036 N was observed demonstrating NC strength and resilience. Therefore, uniform dispersion of 1 wt.% NPs in the polymer matrix increased the welding tensile strength up to 70% of the neat composite.