High-performance textile filament yarns such as para-aramid filament yarn (p-AF) will be used as the base material for the development of sensor yarns (SY) because p-AF offer high tensile strengths and moduli of elasticity, as well as high decomposition temperatures and elongation. However, p-AF has an inert or hydrophobic surface, i.e. a lower polar fraction of the total surface energy that does not allow metallization. The aim of this work is the development of a multifunctional sensor yarn consisting of inert and hydrophobic p-AF. By applying new technologies developed at the Institute of Textile Machinery and Textile High Performance Materials Technology, a homogeneous, completely coated first (1st) and second (2nd) silver layer was built on the p-AF filament yarn surface. The first silver layer monitors the damage in the thermoplastic composite globally and the second silver layer locally. Between two silver layers is an insulation layer. Thus, three layers are built on the p-AF surface. The surface morphology has been determined by light and scanning electron microscopy to assess the Ag layer properties such as structure, homogeneity, and cracking. For structural analysis, p-AF were investigated using a Fourier transform infrared spectrometer. The dispersive and polar component of the surface energy of the treated and pretreated p-AF was measured by using a single fiber Tensiometer (Kruess K100. The Ag and insulation layer thickness was determined after coating and metallization. Textile physical tests of the tensile strength, elasticity modulus, elongation at break and filament yarn fineness of the p-AF before and after the silvering were carried out. The length related electrical resistance of the 1st and 2nd silver layer of the p-AF filament yarns was measured by a Multimeter Fluke 45 (Fluka Germany GmbH) with two wire methods.