The plasma coating of glass fibers is an alternative technology to the wet chemical processes employed for the commercial sizing used for glass-fiber-reinforced polymer composites. A polymer-like film prepared by plasma polymerization can be used as a compatible interlayer between the glass fiber and the polymer matrix. The shear stress distribution across the interphase in a fiber-reinforced polymer composite indicates that the interfacial adhesion at the interlayer/fiber interface is the key factor influencing the performance of the polymer composite. The plasma-polymerized tetravinylsilane deposited at an enhanced effective power was tested as an adhesion film on planar glass substrate using a nanoscratch test. The work of adhesion was used as a measure of film adhesion based on the analysis of the scratch mechanics. An enhanced effective power (0.1-10 W) resulted in a film adhesion change only in the region of 30% for plasma-polymerized tetravinylsilane. The addition of oxygen gas to the tetravinylsilane monomer enabled the depositing of films over a wide range of film adhesions. A 3.7-fold increase in film adhesion was revealed for optimized deposition conditions. For a given film, a strong correlation was found between the shear strength of the polymer composite with glass fibers coated by plasma polymer film and the corresponding film adhesion on planar glass substrate determined using the nanoscratch test.