In this work, experimental and numerical investigation of second harmonic generation (SHG) in mesoporous Si/SiO2 nanoparticles has been performed. Experimental results are well-described by simulations. Spectral analysis reveals that SHG efficiency maxima correlate with Mie resonances of Si/SiO2 nanoparticles. Tuning the diameter of the structures the maximum SHG efficiency for required wavelength can be achieved. The nonlinear optical susceptibility of the studied nanoparticles attains values on the order of 1.59×10−14 m2/V, which exceeds that of bulk silicon. Spherical mesoporous Si/SiO2 nanoparticles demonstrate effective second harmonic generation with simple, low-cost fabrication, making them promising candidates as tunable frequency converters for integrated nanophotonic circuits.