Defects significantly affect the mechanical properties of materials. However, quantitatively correlating the point defects with mechanical property could be a challenge. In this study, we explore the point defect effects on the structure and property of magnetron sputtered TiN nanocrystalline films (synthesized using different negative bias potential) via a combination of analytical techniques and density functional theory (DFT) calculations. We gain insights into the structural evolution and properties of nanocrystalline films at different length scales. It is found that nanocrystal microstructure and local electronic structure triggered by various point defects remarkably change. Along with the structural evolution and point defect changes, the electrical conductivity and the fracture toughness of TiN are improved. Furthermore, the fracture toughness, Young's modulus, and cleavage energy and stresses for TiN films with different point defect structures are calculated. The experimental data is in excellent agreement with first-principle calculations. Our results suggest a direct correlation of the point defect structure with TiN films' mechanical properties.