Metallic nanoparticles are widely used to enhance the electrical conductivity of functional materials. However, despite extensive experimental and theoretical research, further improvement of their conductive performance and the development of low-temperature fabrication processes remain necessary. In this work, we report a UV–Vis-assisted, low-temperature sintering strategy for conductive coatings composed of nickel@silver (Ni@Ag) core–shell nanoparticles and size-controlled silver nanoparticles. The hybrid paste formulation enabled a significant reduction in electrical resistivity, with smaller Ag nanoparticles (10 nm) providing the highest conductivity due to enhanced particle coalescence and improved film densification. An optimal Ag nanoparticle content of 1.5 wt% resulted in coatings with a resistivity of 16 µΩ·cm, corresponding to 46% of the bulk conductivity of nickel and exceeding the performance of undoped Ni@Ag films. This scalable and non-destructive approach offers an effective route for fabricating high-conductivity coatings at low processing temperatures. This scalable, non-destructive process offers a viable route for printed conductive circuits on heat-sensitive substrates.