Novel crystals of pure nickel cadmium oxalate (NCO) and calcium-doped nickel cadmium oxalate (CNCO) were grown by single diffusion method in silica hydrogel by optimizing the growth parameters. The grown crystals were characterized using field-emission scanning electron microscope, energy-dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscope, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and UV–visible spectrometer. Ca 2+ ions were used to occupy the vacancies of intrinsically available Ni 2+ and Cd 2+ ions in the lattice of NCO crystals. This causes change in morphology of NCO crystals and resulted in the growth of CNCO. Crystallinity and lattice parameters of the grown crystals are analysed by XRD technique. Thermal studies show the thermal stability of grown crystals. Number of water molecules present and molecular weight of the crystals were also determined using EDX and TGA studies. Electrical susceptibility, real and imaginary parts of the dielectric constant, energy gap of the as-grown crystals were calculated using the UV–visible spectroscopy. The results of doped crystal were compared with undoped NCO crystal.