Silicon oxynitride layers have been widely used to tailor the optical performance and mechanical resistance of multilayer optical coatings. The key issue for their reliable large-scale application on a glass substrate is the effect of technological parameters on their performance. Here we report on the interrelationship between the conditions of the reactive magnetron deposition process and composition, structure and in turn optical and mechanical properties. The process gas composition and pressure level exhibit a strong influence on the film properties, whereas only moderate effect of magnetron power was observed. The O/(O+N) ratio of the films changes from 0.33 to 0.90 and the film density varies between 2.66 g.cm−3 and 1.85 g.cm−3 along with the increase in the process gas pressure from 0.58 Pa to 1.02 Pa. The refractive index shifts between 1.81 and 1.48 and the residual stress of the film varies in the range from compressive (−385 MPa) to tensile (26 MPa). Hardness and reduced modulus follow the same trend and decline with the increase in process pressure from 12.1 GPa to 2.1 GPa and from 120.3 to 31.6 GPa, respectively. The abrasive wear resistance decreases with the nitrogen content in the films.