The purpose of this study is to observe effect of incorporating vapor-grown carbon nanofibers with various amounts in polyvinylidene fluoride matrix in terms of mechanical strength and electromagnetic shielding effectiveness. Thermoplastic conductive nanocomposites were prepared by heat-pressed compression molding. Vapor-grown carbon nanofibers were utilized at various weight ratios (1wt.%, 3wt.%, 5wt.%, and 8wt.%) as conductive and reinforcing materials. Polyvinylidene fluoride was used as a thermoplastic polymer matrix. Scanning electron microscopic analysis was conducted in order to characterize the morphology and structural properties of the nanocomposites and results revealed well dispersion of carbon nanofibers within the matrix for all concentrations. Mechanical characteristics were investigated according to standards. Findings proved that overall increments of 16%, 37.5%, and 56% were achieved in terms of tensile strength, elasticity modulus, and impact energy, respectively, where a total reduction of 44.8% was observed in terms of elongation for 8wt.% vapor-grown nanofiber matrix compared to that of 0wt.%. Electromagnetic shielding effectivenesses of the nanocomposites were determined by standard protocol using coaxial transmission line measurement technique in the frequency range of 15-3000 MHz. It was observed that resistance, sheet resistance, and resistivity of nanocomposites depicted substantial reduction with the increment in nanofiber content. Nevertheless, it was observed that nanofiber content, dispersion, and network formation within the composites were highly influent on the electromagnetic shielding effectiveness performance of the structures.