With wearable smart textiles playing an increasingly important role in people's life, aramid fiber (AF) stands out among high-performance materials due to its outstanding flexibility, high strength, and impact resistance. However, its excellent insulation makes it unable to sense and respond to external stimuli, which seems to be a call to multiwalled carbon nanotubes (MWCNTs) with high conductivity. In this paper, the effect of MWCNTs in enhancing the electrical properties and interfacial strength of aramid fiber reinforced polymer (AFRP) composites was researched. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) proved that the polydopamine (PDA) layer and MWCNTs were successfully grafted onto the surface of the AF. Scanning electron microscopy (SEM) showed that the distribution of MWCNTs on the fiber surface is quite uniform and dense. As a result, the adhesion of PDA is more conducive to the deposition of MWCNTs, compared with the pristine aramid fiber. The modified fiber AF-PDA-MWCNTs obtained a resistance on the order of 104 MΩ without reducing its mechanical properties (the tensile strength has obtained an increase of 10.59%). The composite material may also have good interface properties, with the interlaminar fracture toughness GI increased by 200.99%. After being endowed with electrical properties, aramid fibers have strong potential in wearable textiles due to their flexibility, high sensitivity to various deformations, and excellent safety protection performance.