Surfactant-free multifunctional semiconductor-metallic nanostructures possessing several modalities are formed due to laser-induced structural modification of pure silicon nanoparticles in the presence of gold. It results to variable size-dependent chemical composition examined by energy-dispersive X-ray spectroscopy. Laser-synthesized silicon-based nanocomposites exhibit remarkable both plasmonic and paramagnetic properties. Their plasmonic maxima are found to be easily adjusted in the whole visible spectral range. Influence of resonant laser irradiation on spin behaviour of silicon-gold nanoparticles is established. Their spin–lattice and spin–spin relaxation processes are investigated as well. Such multifunctional nanoparticles can reveal a huge potential for different applications in field of nanomedicine, in particular, for biosensing and bioimaging.