The main goal of this study was based on estimating the influence of Si3N4 reinforcement nanoparticles on the mechanical and electrochemical properties of Ni-Co-Si3N4 nanocomposite coatings. Ni-Co-Si3N4 nanocomposite coatings were electrodeposited on copper from a modified Watts bath containing Si3N4 particles by direct current (DC). The effect of Si3N4nano-particles on the properties of Ni-Co coatings was studied. Surface morphology, chemical composition, grain size and corrosion resistance of Ni-Co and Ni-Co-Si3N4 nanocomposite coatings were investigated by scanning electron microscope (SEM), energy dispersive X-ray detector (EDS) coupled with SEM, X-ray diffraction analysis (XRD) and electrochemical impedance measurements, respectively. It was found that surface morphologies of NiCo coatings were changed by using nano-particles. There was no difference in the microstructure of coatings, both electrodeposited Ni-Co and Ni-Co-Si3N4 nanocomposite coating's crystalline structure was face-centered cubic (FCC). Based on impedance measurements, it revealed that the corrosion resistance of nanocomposite coatings was more than that of electrodeposited Ni-Co coating. The microhardness of the nanocomposite coatings (678 HV) was higher than that of Ni-Co (580 HV) due to dispersion-strengthening and matrix grain refining. The best mechanical and corrosion resistance properties achieved at the Ni-Co-7.9 wt% Si3N4 nanocomposite coating.